Preparation Method and Application of a Metal Oxide Colloidal Nanocrystal-Based Electrochromic Nanofiber Membrane

Abstract

The present invention belongs to the technical field of flexible electrochromic devices, and relates to a preparation method and application of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane. The preparation method is as follows: A mixed solution of a polymer and metal oxide colloidal nanocrystals is prepared and used as a spinning solution, and an electrochromic nanofiber membrane based on metal oxide colloidal nanocrystals is obtained by electrospinning. The metal oxide colloidal nanocrystals have an organic-inorganic hybrid structure, and the surface of the metal oxide colloidal nanocrystals is provided with oxygen-containing organic functional group ligands. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal metal oxide is 4-8:1. In the prepared colloidal nanocrystal-based electrochromic nanofiber membrane, the particle size of the metal oxide colloidal nanocrystals is 1 / 5-1 / 2 of the fiber diameter. It is applied to wearable devices, smart displays, electronic tags, and smart windows and window films. The method of the present invention is simple and easy to implement, and the prepared product has good electrochromic cycle stability and mechanical stability, and a wide range of applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible electrochromic devices, and relates to a preparation method and application of an electrochromic nanofiber membrane based on metal oxide colloidal nanocrystals. Background Art

[0002] In the field of flexible electrochromic devices, when dealing with the problems of low color display efficiency and long response time in the prior art, generally, composite conductive metal elements (such as nano silver, lanthanum) are used or electrochromic active materials are coated in highly conductive electrodes. Although to a certain extent, the propagation path of conductive particles in the electrochromic process is shortened and the ion transport efficiency is enhanced, the doping substances need to have an atomic size approximate to that of the electrochromic active substances, so the selection range is limited, and it affects the overall electrochromic performance of the device. Moreover, most devices coat electrochromic active materials on rigid substrates, such as indium tin oxide glass (ITO glass), iron tin oxide glass (FTO glass), and there is still insufficient exploration in flexible electrochromic devices.

[0003] Chinese Patent CN202411095052.1 discloses a preparation method of mixing and electrospinning a solid electrolyte and a polymer. After compounding the two, a composite material is obtained. Although this method composites inorganic materials and polymers, the compatibility between the inorganic materials and polymers is poor, which may lead to unstable performance of the composite material. In practical applications, the active components in the composite material may fall off.

[0004] Chinese Patent CN202311657686.7 discloses a piezoelectric nanofiber for sensing by compounding a molecular piezoelectric body / PVDF and its preparation method. A core-shell structured nanofiber is prepared by coaxial electrospinning. The molecular piezoelectric body is used as the shell layer and the fiber is used as the core layer. There are limitations in the interfacial compatibility between the two, so the material selection is limited. The core-shell electrospinning process is complex and difficult to control, and the outer layer material is prone to aging and falling off after long-term use, exposing the internal core layer and affecting the performance stability of the active material itself and the internal core layer.

[0005] Chinese Patent CN115839030A discloses a preparation method of electrochromic fibers that can be woven. An electrochromic slurry is regulated with conductive polymers and pigments, and electrochromic fibers are obtained by impregnating hydrophilic and lipophilic fibers with metal fibers or carbon fibers as current collectors and drying. The color change range of the fibers can be determined by the type, concentration, chromaticity, color, and type of the conductive polymer. However, the interfacial bonding between the fibers obtained by this method and the electrochromic coating is poor, the coating is unevenly dispersed and prone to falling off.

[0006] The Chinese patent CN115652612A discloses an electrochromic fiber and its preparation method. Using a flexible conductive fiber as the substrate, an electrochromic material is deposited on the surface of the substrate by a three-electrode system, so that a dense electrochromic layer is formed on the surface of the flexible conductive fiber. Finally, the electrochromic layer is completely coated with a gel electrolyte, and the electrochromic fiber is obtained after curing. This electrochromic fiber can display different colors with voltage changes, but the surface modification treatment of the conductive fiber is relatively difficult, and the electro-polymerization reaction on the surface of the modified fiber is not easy to accurately control. The purity of the electro-polymerization product is low, and the preparation cost is relatively high.

[0007] The Chinese patent CN117465092A discloses a lanthanum-doped tungsten oxide hydrogen-sensitive color-changing thin film and its preparation method. Ammonium metatungstate, lanthanum nitrate, and polyvinylpyrrolidone are dissolved in deionized water, electrospun, calcined, and cooled to obtain a lanthanum-doped tungsten trioxide composite nanofiber membrane, which is then compounded and cured with a modified silicone resin film to obtain a lanthanum-doped tungsten oxide hydrogen-sensitive color-changing thin film. The method mentioned above improves the conductivity of the thin film by doping lanthanum. The radius of the conductive metal atom needs to be close to that of tungsten oxide to better combine and disperse with tungsten oxide. Therefore, the selection of conductive metal types is limited, and during the casting film process, it is not easy to control the thickness of the film, which affects the insertion and extraction of conductive particles during the redox process, and the cycle stability is poor.

[0008] In summary, the existing flexible electrochromic fiber preparation technology faces the following main problems:

[0009] (1) Loading the active material onto the polymer fiber is only to prepare a composite functional material or to adjust it to a core-shell structure through the electrospinning process. The process is difficult to control, the compatibility between the active material and the polymer is poor, it is easy to fall off during use, and the stability is poor.

[0010] (2) The surface modification of the conductive fiber is difficult, the surface modification efficiency is low, and the electro-polymerization process control and cost are high.

[0011] (3) Loading the active material on the fiber surface in the form of coating or spraying, the binding force between the two is weak, and it is difficult to make the coating thickness uniform.

[0012] (4) Poor performance and mechanical stability, as well as limited material selection.

[0013] These above problems seriously affect the performance and mechanical stability of flexible electrochromic fibers during long-term use.

[0014] Therefore, it is of great significance to study a preparation method and application of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane to solve the problems existing in the prior art. Summary of the Invention

[0015] The object of the present invention is to solve the problems existing in the prior art and provide a preparation method and application of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane.

[0016] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0017] A preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane, which comprises preparing a mixed solution of a polymer and metal oxide colloid nanocrystals as a spinning solution, and obtaining the metal oxide colloid nanocrystal-based electrochromic nanofiber membrane through electrospinning;

[0018] The metal oxide colloid nanocrystals have an organic-inorganic hybrid structure, and the surface of the metal oxide colloid nanocrystals is provided with oxygen-containing organic functional group ligands. The oxygen-containing organic functional group ligands are alkoxide groups, hydroxyl groups and metal-O-carbon bonds. The alkoxide groups are 2-hydroxy-propoxy (-OCH2CHOHCH3), isopropoxy (-OCH(CH3)2), hydroxy-ethoxy (-OCH2CH2OH), 3-hydroxy-propoxy (-OCH2CH2CH2OH), butoxy (-O(CH2)3CH3) or isobutoxy (-OCH2CH(CH3)2), and the mass ratio of the metal oxide inside the surface oxygen-containing organic functional group ligands is 4-8:1;

[0019] The particle size of the metal oxide colloid nanocrystals is 6-40 nm; in the metal oxide colloid nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 30-200 nm, and the particle size of the metal oxide colloid nanocrystals is 1 / 5-1 / 2 of the fiber diameter;

[0020] The present invention adopts a method of mixing electrospinning of metal oxide colloid nanocrystals and organic polymers, and obtains a "semi-embedded" structure in which the metal oxide colloid nanocrystals are uniformly loaded on the surface of the polymer fibers by controlling the surface functional group content of the metal oxide colloid nanocrystals, the proportion of the metal oxide in the polymer, the evaporation rate of the spinning solvent, and controlling the process parameters in electrospinning.

[0021] The structure in which metal oxide colloidal nanocrystals are uniformly loaded on the surface of polymer fibers can ensure that the active material (metal oxide colloidal nanocrystals) can quickly contact ions and charges in the electrolyte, ensuring a rapid response to the electrochromic reaction. Moreover, the ligands on the surface of the metal nanocrystals can be tightly anchored on the polymer fibers, effectively improving the problem of poor binding and easy detachment between the active material and the substrate. This can not only ensure the flexibility of the fibers used but also prevent the detachment of the loaded active material. During electrochromism, it can quickly contact ions and charges in the electrolyte to undergo an electrochemical reaction, ensuring a rapid response, high color rendering efficiency, and good electrochemical reaction activity of the active material in electrochromism. The finally prepared electrochromic fibers feature rapid response, strong mechanical and electrochemical stability, uniform color change, and low-voltage driving. In addition, these electrochromic fibers can be easily woven into fabrics to achieve an intelligent color-changing effect. Through low-voltage stimulation, the fabric can exhibit diverse color changes in different environments, with high flexibility and good wearability.

[0022] Control of the Size and Proportion of Surface Functional Groups of Colloidal Nanocrystals: The size of colloidal nanocrystals and the proportion of surface oxygen-containing organic functional group ligands directly affect their interaction with polymer substrates (such as PVDF), such as strong hydrogen bonds, polar interactions, or electrostatic interactions. When the particle size of metal oxide colloidal nanocrystals is relatively large (such as exceeding 1 / 2 of the fiber diameter), its volume is relatively large compared to the fiber. The colloidal nanocrystals no longer merely stay on the fiber surface but may penetrate into the interior of the fiber, equivalent to penetrating into the fiber interior, and the proportion of the volume entering the fiber is relatively large, forming a state where the active material and the polymer fiber are uniformly mixed, unable to achieve the purpose of uniformly loading metal oxide colloidal nanocrystals on the surface of the polymer fiber; when the nanocrystal particle size is small (such as less than 1 / 5 of the fiber diameter), although the nanosize can make the nanocrystals tend to be on the object surface due to the introduction of organic ligands and are not easily penetrated, due to the too small nanosize, the interaction between its surface organic ligands and the polymer fiber is limited, and it is carried into the fiber interior. Therefore, when the particle size of metal oxide colloidal nanocrystals is 1 / 5 - 1 / 2 of the fiber diameter, the surface tension and surface energy of the fiber surface have a greater impact on the nanocrystals. Metal oxides are more inclined to adhere to the fiber surface in terms of surface energy and interaction force and are not easily penetrated into the fiber pores. By controlling the proportion of surface organic functional groups, the mass ratio of surface oxygen-containing organic functional groups to colloidal nanocrystals is controlled at 4 - 8:1. Under this ratio, the surface of the metal nanocrystals has enhanced surface hydrophobicity, and the surface functional groups can have strong hydrogen bonds, polar interactions, or electrostatic interactions with PVDF. At the same time, by controlling the spinning solution concentration and spinning process parameters, under the action of an electric field, the nanocrystals only exist in the outer layer of the polymer fiber and do not enter the interior, forming a "semi-embedded" structure. The presence of surface oxygen-containing organic functional groups makes the surface energy of the nanocrystals closer to the surface energy of the polymer fiber surface, thereby reducing the possibility of the nanocrystals penetrating into the fiber interior. In addition, the organic oxygen-containing functional group ligand layer forms strong hydrogen bonds, polar interactions, or electrostatic interactions with the polymer matrix, which can improve the interfacial compatibility between the nanocrystals and the polymer matrix, enable the nanocrystals and the polymer to form better interfacial adhesion, and enhance the surface adsorption effect.

[0023] Control of the Nanofiber Diameter and Nanocrystal Distribution: The composition and proportion of the spinning solution (the proportion of solvent, polymer, and additive) can affect the viscosity and evaporation rate of the solution. By controlling the composition and proportion of the spinning solution, the fiber formation rate during the electrospinning process can be controlled. Parameters such as voltage, the distance from the nozzle to the collector, and flow rate will significantly affect the electric field strength and fiber morphology during the spinning process, thereby ensuring that the fiber diameter is 30 - 200 nm, and further affecting the loading method of the nanocrystals to control partial embedding without completely entering the fiber interior.

[0024] Through the regulation of the above factors, mutual coordination and cooperation can achieve a better control effect, and a "semi-embedded" composite nanofiber with metal oxides uniformly loaded on the surface of polymer nanofibers can be prepared. "Semi-embedded" means that metal oxide particles are partially embedded in polymer fibers, but still a part is exposed on the fiber surface. Due to the surface organic ligands, the metal oxides can be firmly anchored on the polymer fibers, and at the same time, part of them are exposed on the fiber surface, increasing the active sites. During the electrochromic process, they can directly contact with the external electrolyte, improving the electrochemical response rate.

[0025] As a preferred technical solution:

[0026] For the preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above, the polymer is polyvinylidene fluoride (PVDF), polyethylene oxide, polymethyl methacrylate, polypropylene, polyamide or polyacrylonitrile, the mass fraction of the polymer in the spinning solution is 5-20%, and the mass ratio of the metal oxide colloidal nanocrystals to the polymer is 1:3-3:1.

[0027] For the preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above, the preparation process of the spinning solution is as follows: adding the polymer into a solvent, stirring at a temperature of 30-50 °C for 4-6 h to obtain a polymer solution, then adding the metal oxide colloidal nanocrystals into the same solvent, stirring at a temperature of 30-50 °C for 4-6 h to prepare a metal oxide colloidal nanocrystal dispersion with the same mass fraction, and stirring and ultrasonically treating the polymer solution and the metal oxide colloidal nanocrystal dispersion at room temperature for 0.5-5 h to obtain the spinning solution.

[0028] For the preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above, the preparation steps of the metal oxide colloidal nanocrystals are as follows:

[0029] (1) Adding a metal precursor into deionized water, stirring at room temperature until it becomes clear to obtain a metal ion solution, and dropping an acidic regulator into the metal ion solution at a rate of 0.2-0.3 mL / min without obvious precipitation during the process;

[0030] (2) Under stirring conditions, a growth template agent is added dropwise to the system in step (1) at a rate of 1-2 mL / min. After the addition is completed, stirring is continued for 0.5-3 h until it becomes clear, and then it is transferred to a hydrothermal reaction kettle with a PTFT inner core and reacted at 90-120 °C for 3.5-5 h; the growth template agent is a short-chain alcohol molecule with 2-4 carbon atoms, such as ethylene glycol, isopropyl alcohol, propylene glycol, 1,3-propanediol, n-butanol, isobutanol; by adding the growth template agent, during the synthesis process, some derivatives and hydrolysis products of the template agent bind to the surface of the metal oxide. Therefore, a stable molecular layer is formed on the surface of the crystal nucleus, that is, it has alkoxide groups, hydroxyl groups, and metal-O-carbon bonds on the surface, so stable dispersed metal oxide colloidal nanocrystals are formed in the liquid phase. The ligands formed on the surface of the nanocrystals after the reaction of the short-chain alcohol molecules enhance the surface hydrophobicity, which is suitable for dispersion in organic media;

[0031] (3) After the reaction in step (2) is completed, it is cooled and centrifugally washed with deionized water until the pH of the supernatant is 6.5-7. Then, deionized water is continuously added, and the upper colloidal solution (showing the Tyndall effect) is continuously collected at a rotation speed of 4000-7000 r / min until the Tyndall effect no longer appears in the supernatant;

[0032] (4) The colloidal solution collected in step (3) is transferred into a dialysis bag with a molecular weight cut-off of 3000-5000 and dialyzed for 5-7 days to remove impurities;

[0033] (5) The metal oxide colloidal nanocrystals are obtained by freeze-drying the dialyzed colloidal solution.

[0034] In the preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above, in step (1), the metal precursor is one or more of sodium tungstate, ammonium metatungstate, ammonium tungstate, tetrabutyl titanate, titanium tetrachloride, ammonium vanadate, sodium vanadate, and vanadium chloride.

[0035] In the preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above, in step (1), the acidic regulator is one or more of hydrochloric acid, nitric acid, oxalic acid, and acetic acid.

[0036] In the preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above, in step (1), the concentration of the metal ion solution is 0.2-0.6 mol / L, and the molar ratio of the metal ion to the hydrogen ion in the acidic regulator is 1:1-2; in step (1), the molar ratio of the metal ion to the growth template agent in step (2) is 1:2-6.

[0037] A method for preparing a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane as described above. The needle gauge used in electrospinning is 20 - 22 G. A roller is used as the receiving device, the receiving distance is 10 - 15 cm, the lateral reciprocating distance of the needle is 80 - 120 mm, the moving speed is 0.3 - 0.5 cm / s, and the electrospinning voltage is 16 - 20 kV.

[0038] Determine the appropriate voltage according to the concentration of the spinning solution. After setting, start the electrospinning machine for spinning. After spinning is completed, turn off the high-voltage power supply and dry it in vacuum at 60 °C for 12 h to remove the solvent. Subsequently, perform structural characterization and performance testing on the dried nanofiber membrane.

[0039] The present invention also provides an application of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane prepared by the method described in any one of the above. It is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

[0040] The fields where the metal oxide colloidal nanocrystal electrochromic nanofiber membrane of the present invention can be applied:

[0041] 1. Wearable devices, such as being applied to smart clothing or electronic skin, can change their own color and transparency through external conditions, such as changes in temperature and light intensity, to achieve intelligent color conversion and adaptive functions;

[0042] 2. Smart displays and electronic tags. For example, through the electrochromic effect, an electronic tag can update the displayed text or image in a timely manner according to needs at a low voltage, reducing manual operation and improving efficiency;

[0043] 3. Smart windows and window films, mainly by adjusting transparency to optimize indoor lighting, temperature, and privacy protection. For example, when the light is too strong and a voltage is applied, the transparency of the window film changes, blocking sunlight and reducing the indoor temperature, preventing ultraviolet rays from entering, achieving an energy-saving effect; it can also be used as a window film to dim when needed to protect privacy.

[0044] Beneficial effects:

[0045] (1) The preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane of the present invention has uniformly distributed particle sizes of metal oxide colloidal nanocrystals. The addition of surface oxygen-containing organic functional group ligands increases the proportion of oxygen-containing functional groups on the surface of metal oxide nanoparticles, has high dispersibility in solvents, and forms stable interfacial interactions with the polymer matrix. The magnitude of the interaction is slightly smaller than the intermolecular interaction of the polymer. Finally, a structure in which metal oxide colloidal nanocrystal particles are dispersed on the nanofiber surface in a "semi-embedded" form is prepared, which is different from the structures where colloidal nanocrystals are only loaded or grafted on nanofibers and where colloidal nanocrystals are dispersed on the surface and inside of nanofibers. This improves the interfacial compatibility between the nanocrystals and the polymer matrix, enables better interfacial adhesion between the nanocrystals and the polymer, and enhances the surface adsorption effect.

[0046] (2) The preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane of the present invention realizes the uniform dispersion and stable binding of colloidal nanocrystals on nanofibers, making them not easy to fall off and improving stability. In addition, the present invention is aimed at electrochromic functional fiber membranes. Under electrochemical conditions, the co-insertion / extraction of electrons and ions leads to reversible changes in the optical absorption properties of the active material, endowing the fiber membrane with electrochromic activity. Therefore, the active material needs to be exposed on the surface of the nanofiber to exhibit more obvious optical changes in the electrochemical system. At the same time, the uniform dispersion and loading of nanocrystals on the surface of nanofibers ensure the migration path of electrons and ions in the fiber membrane. The prepared electrochromic fiber membrane has the characteristics of high color display efficiency, fast response speed, good electrochromic cycle stability, and good mechanical stability.

[0047] (3) The preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane of the present invention uses a low-temperature hydrothermal method. By controlling the molar ratio of metal ions to hydrogen ions in the acidic regulator, temperature, and time, controllable oxygen-containing functional group content, particle size distribution, and morphological characteristics are achieved. Compared with the existing technology, the process is safer and has lower costs, and is suitable for large-scale preparation.

[0048] (4) The application of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane of the present invention is for industrial applications and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 FIG. is a schematic structural diagram of tungsten oxide colloidal nanocrystals loaded on polymer fibers (MO Figure 2 , , ,

[0050] ,

[0049] , x , Figure 1 CNCs@PF) in Example 1, where the white spheres represent tungsten oxide colloidal nanocrystals;

[0050] Figure 2 FIG. is a scanning electron microscope image of tungsten oxide colloidal nanocrystals@polyvinylidene fluoride nanofibers in Example 1. Detailed implementation manners

[0051] The present invention will be further described below in conjunction with specific implementation manners. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0052] The test methods for the performance indicators in the embodiments and comparative examples of the present invention are as follows:

[0053] Electrochromic performance: including response time (coloring time, fading time), coloration efficiency, and optical modulation range response time; the response time can be obtained by electrochemical test method - chronoamperometry (CA), the optical modulation range can be obtained by ultraviolet-visible spectrophotometer (UV-vis), and the coloration efficiency can be calculated from the data of cyclic voltammetry (CV) and ultraviolet-visible spectrophotometer (UV-vis);

[0054] The calculation formula for the coloration efficiency (Coloration Efficiency, CE) is as follows:

[0055] CE = ΔOD / Q;

[0056] Wherein, ΔOD is the change in optical density, dimensionless, and can be calculated from the ultraviolet spectrum data according to ΔOD = OD colored −OD bleached = log(T bleached / T colored ); OD colored is the optical density in the colored state, OD bleached is the optical density in the faded state, T bleached is the light transmittance in the faded state, T colored is the light transmittance in the colored state; Q is the charge amount, with the unit of coulomb (C), and can be obtained from the data of chronoamperometry (CA), Q = ∫I(t) dt, where I is the current and t is the time.

[0057] Optical modulation range: refers to the difference in transmittance between the colored state and the faded state of the material at 633 nm after applying voltage, that is, T bleached -T colored .

[0058] Cycling stability performance: obtained by chronoamperometry (CA), and record the change in the optical modulation range of the metal oxide colloid nanocrystal-based electrochromic nanofiber membrane during 5000 cycles.

[0059] Sources of some substances in the present invention:

[0060] Polyvinylidene fluoride: Manufacturer: Shanghai Titan Co., Ltd., Grade: Adamas; Average molecular weight 850,000.

[0061] Polyethylene oxide: Manufacturer: Shanghai Titan Co., Ltd., Grade: Adamas; Viscosity-average molecular weight 100,000.

[0062] Polymethyl methacrylate: Manufacturer: Shanghai Titan Co., Ltd., Grade: Sigma-Aldrich; Weight-average molecular weight 120,000.

[0063] Polypropylene: Manufacturer: Merck Chemical Technology (Shanghai) Co., Ltd., Grade: Sigma-Aldrich; Weight-average molecular weight 250,000.

[0064] Nylon 6: Manufacturer: Sigma-Aldrich, Weight-average molecular weight 100,000.

[0065] Nylon 66: Manufacturer: Shanghai Yuanye Bio-Technology Co., Ltd., Weight-average molecular weight 100,000.

[0066] Nylon 11: Manufacturer: Shanghai Yuanye Bio-Technology Co., Ltd., Weight-average molecular weight 80,000.

[0067] Polyacrylonitrile: Shanghai Titan Co., Ltd., Grade: Adamas; Weight-average molecular weight 150,000.

[0068] Example 1

[0069] A preparation method of an electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals, the specific steps are as follows:

[0070] (1) Preparation of raw materials:

[0071] Metal precursor: Sodium tungstate;

[0072] Polymer: Polyvinylidene fluoride;

[0073] Acidic regulator: 0.22 mol / L hydrochloric acid;

[0074] Growth template agent: 1,2-propanediol;

[0075] Solvent: Deionized water;

[0076] (2) The preparation steps of tungsten oxide colloidal nanocrystals are as follows:

[0077] (2.1) Add the metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution with a concentration of 0.2 mol / L, and dropwise add the acidic regulator to the metal ion solution at a rate of 0.2 mL / min;

[0078] Among them, the molar ratio of the metal ions to the hydrogen ions in the acidic regulator in step (2.1) is 1:1.25;

[0079] (2.2) Under stirring conditions, a growth template agent is added dropwise to the system in step (2.1) at a rate of 1 mL / min. After the addition is completed, stirring is continued for 0.5 h until it becomes clear, and then it is transferred to a hydrothermal reaction kettle with a PTFT inner core and reacted at 100 °C for 5 h;

[0080] Among them, the molar ratio of the metal ions in step (2.1) to the growth template agent in step (2.2) is 1:3;

[0081] (2.3) After the reaction in step (2.2) is completed, it is cooled and centrifugally washed with deionized water until the pH of the supernatant is 6.5. Then, deionized water is continuously added, and the upper colloidal solution is continuously collected at a rotation speed of 4000 r / min until there is no Tyndall phenomenon in the supernatant;

[0082] (2.4) The colloidal solution collected in step (2.3) is transferred into a dialysis bag with a molecular weight cut-off of 3000 Da and dialyzed for 5 days;

[0083] (2.5) The tungsten oxide colloidal nanocrystals with an average particle size of 15 nm are obtained by freeze-drying the dialyzed colloidal solution;

[0084] The tungsten oxide colloidal nanocrystals have an organic-inorganic hybrid structure. The surface of the tungsten oxide colloidal nanocrystals is provided with oxygen-containing organic functional group ligands. The oxygen-containing organic functional group ligands are 2-hydroxy-propoxy group, hydroxyl group and metal-O-carbon bond. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal tungsten oxide is 4:1;

[0085] (3) Preparation of the spinning solution:

[0086] The polymer is added to the solvent, and stirred at a temperature of 30 °C for 6 h to obtain a polymer solution. Then, the tungsten oxide colloidal nanocrystals are added to the same solvent, and stirred at a temperature of 30 °C for 6 h to prepare a tungsten oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the tungsten oxide colloidal nanocrystal dispersion are stirred at room temperature and ultrasonically treated for 0.5 h to obtain the spinning solution;

[0087] The mass fraction of the polymer in the spinning solution is 5%, and the mass ratio of the tungsten oxide colloidal nanocrystals to the polymer is 1:3;

[0088] (4) The spinning solution in step (3) is electrospun to obtain a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane;

[0089] The process parameters are as follows: The needle size used for electrospinning is 20 G. A roller is used as the receiving device, the receiving distance is 10 cm, the lateral reciprocating distance of the needle is 80 mm, the moving speed is 0.3 cm / s, and the spinning voltage is 16 kV.

[0090] In the finally prepared tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the average fiber diameter is 50 nm, and the particle size of the tungsten oxide colloidal nanocrystals is 3 / 10 of the fiber diameter; the coloring time of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 7 s, the fading time is 3 s, the optical modulation range at 633 nm is 35%, and the coloring efficiency is 40 C / cm 2 ; After 3000 cycles, the optical modulation range of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 85% of the initial optical modulation range.

[0091] The tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

[0092] As Figure 1 shown, it is a schematic structural diagram of tungsten oxide colloidal nanocrystals loaded on the surface of polymer fibers (MO x CNCs@PF) in Example 1, where the white spheres represent tungsten oxide colloidal nanocrystals. The tungsten oxide colloidal nanocrystals are uniformly loaded onto the polymer fiber membrane. Half of the tungsten oxide colloidal nanocrystals are embedded in the fibers, and half are exposed to the external environment, presenting a "semi-embedded" structure. Therefore, during the electrochromic process, the active materials exposed outside can quickly contact ions and charges in the electrolyte, ensuring a rapid response to the electrochromic reaction. Moreover, the ligands on the surface of the tungsten oxide colloidal nanocrystals can be tightly anchored on the polymer fibers, effectively improving the problem of poor binding and easy detachment between the active materials and the substrate.

[0093] As Figure 2 shown, it is the scanning electron microscope of tungsten oxide colloidal nanocrystals@polyvinylidene fluoride nanofibers in Example 1. It can be Figure 2 seen that the fiber diameters are relatively uniform, and the average fiber diameter is 50 nm. The fiber surface is relatively smooth, without crack and void defects. The doped tungsten oxide nanocrystals are uniformly loaded on the fiber surface without aggregation and caking phenomena, which helps to improve the overall electrochromic performance of the fibers.

[0094] Comparative Example 1:

[0095] A preparation method of an electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals is basically the same as that of Example 1, except that the particle size of the tungsten oxide colloidal nanocrystals is 5 nm. The implementation method is as follows: by controlling the molar ratio of metal ions to hydrogen ions in the acidic regulator in step (2.1) to be 1:3, and the reaction temperature in step (2.2) to be 70 °C.

[0096] The coloring time of the finally prepared electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals is 10 s, the fading time is 6 s, and the coloring efficiency is 25 C / cm 2 .

[0097] Comparing Comparative Example 1 with Example 1, it can be found that the coloring time and fading time of the electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals in Comparative Example 1 both increase, the response speed becomes slower, and the coloring efficiency decreases. This is because the decrease in temperature and the increase in hydrogen ion concentration limit the growth of grain size, generating nanocrystals with smaller particle size. Although the nanocrystals with smaller particle size can be biased towards the object surface due to the introduction of organic ligands and are not easy to enter, due to the too small nanosize, the interaction force between the organic ligands on its surface and the polymer fiber is limited and it is carried into the fiber interior. Therefore, during the electrochromic process, it cannot quickly contact the charge and ions in the electrolyte, and the increase in the organic matter content on the crystal surface further increases the resistance to the embedding and migration of ions and charges, resulting in a slowdown in the electrochromic response speed.

[0098] Comparative Example 2:

[0099] A preparation method of an electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals is basically the same as that of Example 1, except that the particle size of the tungsten oxide colloidal nanocrystals is 42 nm. The implementation method is as follows: by controlling the molar ratio of metal ions to hydrogen ions in the acidic regulator in step (2.1) to be 2:1, and the reaction temperature in step (2.2) to be 150 °C.

[0100] The coloring time of the finally prepared electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals is 11 s, the fading time is 6 s, and after 3000 cycles, the optical modulation range of the electrochromic nanofiber membrane decays to 65% of the initial optical modulation range.

[0101] Comparing Comparative Example 2 with Example 1, it can be found that in Comparative Example 2, the coloring time and fading time of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane during the electrochromic process increase, the response speed slows down, and during 3000 cycles of use, the optical modulation range decays severely; this is because when the concentration of hydrogen ions in the reaction solution decreases and the pH increases, in an acidic environment, the crystal growth environment is more stable and tends to form larger-sized nanocrystals. Tungsten oxide crystals with larger particle sizes have a relatively smaller surface area, resulting in an increase in the resistance to ion diffusion and electron transfer, thereby reducing the rate of the electrochromic reaction; furthermore, it affects the speed of the electrochromic reaction, and with a relatively smaller surface area, the interaction force with the polymer fibers weakens, and it is prone to falling off during the electrochromic cycling process, resulting in a decrease in cycle stability.

[0102] Comparative Example 3:

[0103] A method for preparing a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is basically the same as that of Example 1, except that in the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 25 nm, and the implementation method is: by controlling the mass fraction of the polymer in the spinning solution in step (3) to be 4%, and the spinning voltage in step (4) to be 25 kV.

[0104] The coloring time of the finally prepared tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 9 s, the fading time is 4 s, and the optical modulation range of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 45% of the initial optical modulation range.

[0105] Comparing Comparative Example 3 with Example 1, it can be found that as the concentration of the polymer in the spinning solution decreases and the electrospinning voltage increases, the fiber diameter decreases to 25 nm, and the coloring and fading times of the electrochromic nanofiber membrane increase; due to the fact that thinner fibers are prone to surface damage during the electrochromic process, resulting in a serious decline in stability performance, and after only 3000 cycles, the optical performance decays to 45% of the original.

[0106] Comparative Example 4:

[0107] A method for preparing a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is basically the same as that of Example 1, except that in the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 220 nm, and the implementation method is: by controlling the mass fraction of the polymer in the spinning solution in step (3) to be 22%, and the spinning voltage in step (4) to be 12 kV.

[0108] The coloring time of the finally prepared tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 12 s, the fading time is 7 s, the optical modulation range is between 20%, and the coloring efficiency is 25 C / cm 2 ;

[0109] Comparing Comparative Example 4 with Example 1, it can be found that increasing the concentration of the polymer in the spinning solution and decreasing the spinning voltage can form thicker fibers. The electrochromic response speed of the tungsten oxide colloidal nanocrystal-based electrochromic fiber prepared becomes slower. At the same time, the optical modulation range decreases and the coloring efficiency decreases. This is because for a larger fiber diameter, its surface area is relatively small, which limits the diffusion speed of ions in the fiber and restricts the surface contact of active substances, charges and ions during the electrochromic process. And because the particle size of the tungsten oxide colloidal nanocrystals is relatively too small, the interaction force between the surface organic ligands and the polymer fiber is limited and is carried into the fiber interior, reducing the contact with ions and charges. Therefore, the response speed, optical modulation and coloring efficiency are reduced.

[0110] Comparative Example 5:

[0111] A method for preparing a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is basically the same as that of Example 1, except that the mass ratio of the surface oxygen-containing organic functional group ligand to the internal metal oxide is 3:1, that is, the molar ratio of the metal ions in step (2.1) to the growth template agent in step (2.2) is 2:1 (the increase of the growth template agent can increase the proportion of the surface oxygen-containing organic functional groups in the metal oxide colloidal nanocrystals to a certain extent. At this time, increasing the molar ratio of the metal ions and the growth template agent, the content of the growth template agent decreases, so the mass ratio of the surface organic ligand to the internal metal oxide decreases).

[0112] The coloring time of the finally prepared electrochromic nanofiber membrane is 14 s, and the fading time is 6 s; after 3000 cycles, the optical modulation range of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 55% of the initial optical modulation range.

[0113] Comparing Comparative Example 5 with Example 1, it can be found that when the ratio of the ligand decreases, the mass ratio of the surface organic functional group ligand to the core of the metal oxide colloidal nanocrystal decreases, the electrochromic response speed becomes slower, and the cycle stability seriously decreases. On the one hand, due to the decrease in the proportion of the added growth template agent, and because the growth template agent has a certain limiting effect on the particle size of the metal oxide, restricting the growth of the crystal. After the ratio decreases, the particle size of the metal oxide nanocrystal increases, increasing the resistance of ions and charges to embed and migrate out, resulting in a slower response speed; the decrease in the surface ligand ratio reduces the interaction force between the tungsten oxide colloidal nanocrystals and the polymer fiber. During the electrochromic process, the tungsten oxide nanocrystals are likely to fall off, resulting in a serious decrease in cycle stability.

[0114] Comparative Example 6:

[0115] A preparation method of an electrochromic nanofiber membrane is basically the same as that of Example 1, except that the mass ratio of the surface oxygen-containing organic functional group ligand to the internal tungsten oxide is 9:1, that is, the molar ratio of the metal ion in step (2.1) to the growth template agent in step (2.2) is 1:8.

[0116] The coloring time of the finally prepared electrochromic nanofiber membrane is 12 s, the fading time is 6 s, the optical modulation range is within 35%, and the coloring efficiency is 25 C / cm 2 .

[0117] Comparing Comparative Example 6 with Example 1, it can be found that when the molar ratio of the metal ion to the growth template agent increases, both the coloring time and the fading time of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane increase, the response speed becomes slower, and the coloring efficiency decreases; this is because with the increase in the proportion of the growth template agent, a higher concentration of the template agent can reduce the aggregation of metal ions and lower the crystal growth rate, thereby obtaining nanocrystals with smaller particle sizes. When the nanocrystal particle size is small, although the nanocrystals can be biased towards the object surface due to the introduction of organic ligands and are not easily incorporated, due to the too small nanosize, the interaction force between the surface organic ligands and the polymer fibers is limited and they are brought into the fiber interior. Therefore, during the electrochromic process, they cannot quickly contact the charges and ions in the electrolyte, and the increase in the organic matter content on the crystal surface makes it difficult for ions and charges to be embedded and removed, further increasing the resistance to the embedding and removal of ions and charges, resulting in a slowdown in the electrochromic response speed, a decrease in the optical modulation range, and a decrease in the coloring efficiency.

[0118] Example 2

[0119] A preparation method of a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is as follows:

[0120] (1) Preparation of raw materials:

[0121] Metal precursor: ammonium metatungstate;

[0122] Polymer: polyethylene oxide;

[0123] Acid regulator: nitric acid with a concentration of 0.1 mol / L;

[0124] Growth template agent: isopropanol;

[0125] Solvent: deionized water;

[0126] (2) The preparation steps of tungsten oxide colloidal nanocrystals are as follows:

[0127] (2.1) Add the metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution with a concentration of 0.3 mol / L, and dropwise add an acidic regulator to the metal ion solution at a rate of 0.25 mL / min;

[0128] Among them, in step (2.1), the molar ratio of metal ions to hydrogen ions in the acidic regulator is 1:1;

[0129] (2.2) Under stirring conditions, dropwise add a growth template agent to the system in step (2.1) at a rate of 2 mL / min. After the addition is completed, continue stirring for 1 h until clear, transfer it to a hydrothermal reaction kettle with a PTFT inner core, and react at 90 °C for 4.5 h;

[0130] Among them, in step (2.1), the molar ratio of metal ions to the growth template agent in step (2.2) is 1:2;

[0131] (2.3) After the reaction in step (2.2) is completed, cool and centrifugally wash with deionized water until the pH of the supernatant is 6.6. Then continue to add deionized water, and continuously collect the upper colloidal solution at a rotation speed of 5000 r / min until there is no Tyndall phenomenon in the supernatant;

[0132] (2.4) Transfer the colloidal solution collected in step (2.3) to a dialysis bag with a molecular weight cut-off of 3000 Da and dialyze for 6 days;

[0133] (2.5) Collect tungsten oxide colloidal nanocrystals with an average particle size of 40 nm by freeze-drying the dialyzed colloidal solution;

[0134] The tungsten oxide colloidal nanocrystals have an organic-inorganic hybrid structure. The surface of the tungsten oxide colloidal nanocrystals is provided with oxygen-containing organic functional group ligands. The oxygen-containing organic functional group ligands are isopropoxy groups, hydroxyl groups, and metal-O-carbon bonds. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal tungsten oxide is 5:1;

[0135] (3) Preparation of the spinning solution:

[0136] Add the polymer to the solvent, stir at a temperature of 35 °C for 5.5 h to obtain a polymer solution, and then add the tungsten oxide colloidal nanocrystals to the same solvent, stir at a temperature of 35 °C for 5.5 h to prepare a tungsten oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the tungsten oxide colloidal nanocrystal dispersion are stirred at room temperature and ultrasonically treated for 1 h to obtain a spinning solution;

[0137] The mass fraction of the polymer in the spinning solution is 10%, and the mass ratio of the tungsten oxide colloidal nanocrystals to the polymer is 1:1;

[0138] (4) The spinning solution in step (3) is electrospun to obtain a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane;

[0139] The process parameters are as follows: The needle gauge used for electrospinning is 22 G. A roller is used as the receiving device. The receiving distance is 11 cm. The horizontal reciprocating distance of the needle is 90 mm. The moving speed is 0.35 cm / s. The electrospinning voltage is 17 kV.

[0140] In the finally obtained tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 200 nm, and the particle size of the tungsten oxide colloidal nanocrystals is 1 / 3 of the fiber diameter; the coloring time of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 7.2 s, the fading time is 2.3 s, the optical modulation range at 633 nm is within 30%, and the coloring efficiency is 35 C / cm 2 ; After 3000 cycles, the optical modulation range of the tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 86% of the initial optical modulation range.

[0141] The tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

[0142] Example 3

[0143] A preparation method of a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the specific steps are as follows:

[0144] (1) Preparation of raw materials:

[0145] Metal precursor: ammonium tungstate;

[0146] Polymer: polymethyl methacrylate;

[0147] Acidic regulator: oxalic acid with a concentration of 0.1 mol / L;

[0148] Growth template agent: ethylene glycol;

[0149] Solvent: deionized water;

[0150] (2) The preparation steps of the tungsten oxide colloidal nanocrystals are as follows:

[0151] (2.1) Add the metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution with a concentration of 0.4 mol / L, and dropwise add the acidic regulator to the metal ion solution at a speed of 0.3 mL / min;

[0152] Among them, in step (2.1), the molar ratio of the metal ions to the hydrogen ions in the acidic regulator is 1:1.5;

[0153] (2.2) Add the growth template to the system in step (2.1) at a rate of 1.5 mL / min under stirring. Continue stirring for 2 h until the solution becomes clear. Transfer the solution to the hydrothermal reactor of the PTFT core and react at 90 °C for 4 h.

[0154] Wherein, the molar ratio of the metal ion in step (2.1) to the growth template in step (2.2) is 1:4;

[0155] (2.3) After the reaction in step (2.2) is completed, cool and centrifuge with deionized water until the pH of the supernatant reaches 6.7. Continue to add deionized water and continuously collect the upper colloidal solution at a speed of 6000 r / min until the supernatant no longer shows Tyndall phenomenon.

[0156] (2.4) Transfer the colloidal solution collected in step (2.3) to a dialysis bag with a molecular weight cutoff of 4000 Da and dialyze for 7 days;

[0157] (2.5) The dialyzed colloidal solution was freeze-dried and collected to obtain tungsten oxide colloidal nanocrystals with an average particle size of 6 nm;

[0158] Tungsten oxide colloidal nanocrystals have an organic-inorganic hybrid structure. The surface of the tungsten oxide colloidal nanocrystals has oxygen-containing organic functional group ligands. The oxygen-containing organic functional group ligands are hydroxyl-ethoxy, hydroxyl and metal-O-carbon bonds. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal tungsten oxide is 7:1.

[0159] (3) Preparation of spinning solution:

[0160] The polymer was added to the solvent and stirred at 40°C for 5 hours to obtain a polymer solution. Tungsten oxide colloidal nanocrystals were then added to the same solvent and stirred at 40°C for 5 hours to prepare a tungsten oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the tungsten oxide colloidal nanocrystal dispersion were stirred at room temperature and ultrasonically treated for 2 hours to obtain a spinning solution.

[0161] The mass fraction of polymer in the spinning solution is 8%, and the mass ratio of tungsten oxide colloidal nanocrystals to polymer is 1.5:1;

[0162] (4) electrospinning the spinning solution of step (3) to obtain a tungsten oxide colloidal nanocrystal-based electrochromic nanofiber membrane;

[0163] The process parameters are as follows: the needle specification used for electrospinning is 21 G, a roller is used as the receiving device, the receiving distance is 12 cm, the lateral round-trip distance of the needle is 95 mm, the moving speed is 0.4 cm / s, and the spinning voltage is 20 kV.

[0164] In the finally obtained electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals, the fiber diameter is 30 nm, and the particle size of the tungsten oxide colloidal nanocrystals is 1 / 5 of the fiber diameter; the coloring time of the electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals is 8 s, the fading time is 2.8 s, the optical modulation range at 633 nm is 45%, and the coloring efficiency is 50 C / cm 2 ; After 3000 cycles, the optical modulation range of the electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals decays to 86% of the initial optical modulation range.

[0165] The electrochromic nanofiber membrane based on tungsten oxide colloidal nanocrystals is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

[0166] Example 4

[0167] A preparation method of an electrochromic nanofiber membrane based on titanium oxide colloidal nanocrystals, the specific steps are as follows:

[0168] (1) Preparation of raw materials:

[0169] Metal precursor: tetrabutyl titanate;

[0170] Polymer: polypropylene;

[0171] Acidic regulator: acetic acid with a concentration of 0.2 mol / L;

[0172] Growth template agent: 1,3-propanediol;

[0173] Solvent: deionized water; [[ID=3V1]]

[0174] (2) The preparation steps of the titanium oxide colloidal nanocrystals are as follows:

[0175] (2.1) Add the metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution with a concentration of 0.5 mol / L, and dropwise add the acidic regulator to the metal ion solution at a rate of 0.22 mL / min; [[ID=3V2]]

[0176] Among them, the molar ratio of the metal ions to the hydrogen ions in the acidic regulator in step (2.1) is 1:1.5;

[0177] (2.2) Under stirring conditions, dropwise add the growth template agent to the system in step (2.1) at a rate of 1.2 mL / min. After the addition is completed, continue to stir for 3 h until clear, transfer to a hydrothermal reaction kettle with a PTFT inner core, and react at 120 °C for 3.5 h;

[0178] Among them, the molar ratio of the metal ions in step (2.1) to the growth template agent in step (2.2) is 1:5;

[0179] (2.3) After the reaction in step (2.2) is completed, cool and centrifuge-wash with deionized water until the pH of the supernatant is 6.8. Then continue to add deionized water and continuously collect the upper colloidal solution at a rotation speed of 7000 r / min until there is no Tyndall phenomenon in the supernatant;

[0180] (2.4) Transfer the colloidal solution collected in step (2.3) into a dialysis bag with a molecular weight cut-off of 4000 Da and dialyze for 5.5 days;

[0181] (2.5) Collect titanium oxide colloidal nanocrystals with an average particle size of 15 nm by freeze-drying the dialyzed colloidal solution;

[0182] The titanium oxide colloidal nanocrystals have an organic-inorganic hybrid structure. The surface of the titanium oxide colloidal nanocrystals is provided with oxygen-containing organic functional group ligands. The oxygen-containing organic functional group ligands are 3-hydroxy-propoxy, hydroxyl, and metal-O-carbon bonds. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal titanium oxide is 8:1;

[0183] (3) Preparation of the spinning solution:

[0184] Add the polymer to the solvent and stir at 45 °C for 4.5 h to obtain a polymer solution. Then add the titanium oxide colloidal nanocrystals to the same solvent and stir at 45 °C for 4.5 h to prepare a titanium oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the titanium oxide colloidal nanocrystal dispersion are stirred at room temperature and ultrasonically treated for 3 h to obtain a spinning solution;

[0185] The mass fraction of the polymer in the spinning solution is 20%, and the mass ratio of the titanium oxide colloidal nanocrystals to the polymer is 2:1;

[0186] (4) The spinning solution in step (3) is electrospun to obtain a titanium oxide colloidal nanocrystal-based electrochromic nanofiber membrane;

[0187] The process parameters are as follows: The needle gauge used for electrospinning is 20 G. A roller is used as the receiving device. The receiving distance is 13 cm. The transverse reciprocating distance of the needle is 100 mm. The moving speed is 0.45 cm / s. The electrospinning voltage is 16 kV.

[0188] In the finally prepared titanium oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 60 nm, and the particle size of the titanium oxide colloidal nanocrystals is 1 / 4 of the fiber diameter; The coloring time of the titanium oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 7.1 s, the fading time is 2 s, the optical modulation range at 633 nm is 25%, and the coloring efficiency is 35 C / cm 2;After 3000 cycles, the optical modulation range of the titanium oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 88% of the initial optical modulation range.

[0189] The titanium oxide colloidal nanocrystal-based electrochromic nanofiber membrane is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

[0190] Example 5

[0191] A preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane is as follows:

[0192] (1) Preparation of raw materials:

[0193] Metal precursor: Titanium tetrachloride and ammonium metavanadate with a mass ratio of 1:1;

[0194] Polymer: Nylon 6;

[0195] Acidic regulator: Hydrochloric acid with a concentration of 0.22 mol / L;

[0196] Growth template agent: n-Butanol;

[0197] Solvent: Deionized water;

[0198] (2) The preparation steps of the metal oxide colloidal nanocrystals are as follows:

[0199] (2.1) Add the metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution with a concentration of 0.06 mol / L, and dropwise add the acidic regulator to the metal ion solution at a rate of 0.24 mL / min;

[0200] Among them, the molar ratio of metal ions to hydrogen ions in the acidic regulator in step (2.1) is 1:2;

[0201] (2.2) Under stirring conditions, dropwise add the growth template agent to the system in step (2.1) at a rate of 1.4 mL / min. After the addition is completed, continue to stir for 1.5 h until clear, transfer to a hydrothermal reaction kettle with a PTFT inner core, and react at 100 °C for 4.75 h;

[0202] Among them, the molar ratio of metal ions in step (2.1) to the growth template agent in step (2.2) is 1:6;

[0203] (2.3) After the reaction in step (2.2) is completed, cool and centrifuge and wash with deionized water until the pH of the supernatant is 6.9. Then continue to add deionized water, and continuously collect the upper colloidal solution at a rotation speed of 4500 r / min until there is no Tyndall phenomenon in the supernatant;

[0204] (2.4) Transfer the colloidal solution collected in step (2.3) into a dialysis bag with a molecular weight cut-off of 5000 Da and dialyze for 6.5 days;

[0205] (2.5) Collect metal oxide colloidal nanocrystals with an average particle size of 40 nm by freeze-drying the dialyzed colloidal solution;

[0206] The metal oxide colloidal nanocrystals have an organic-inorganic hybrid structure. The surface of the metal oxide colloidal nanocrystals is attached with oxygen-containing organic functional group ligands, and the oxygen-containing organic functional group ligands are butoxy groups, hydroxyl groups, and metal-O-carbon bonds. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal metal oxide is 8:1;

[0207] (3) Preparation of the spinning solution:

[0208] Add the polymer to the solvent and stir at 50 °C for 4 h to obtain a polymer solution. Then add the metal oxide colloidal nanocrystals to the same solvent and stir at 50 °C for 4 h to prepare a metal oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the metal oxide colloidal nanocrystal dispersion are stirred at room temperature and ultrasonically treated for 4 h to obtain a spinning solution;

[0209] The mass fraction of the polymer in the spinning solution is 15%, and the mass ratio of the metal oxide colloidal nanocrystals to the polymer is 3:1;

[0210] (4) The spinning solution in step (3) is electrospun to obtain a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane;

[0211] The process parameters are as follows: The needle gauge used for electrospinning is 21 G. A roller is used as the receiving device, the receiving distance is 14 cm, the horizontal reciprocating distance of the needle is 110 mm, the moving speed is 0.48 cm / s, and the electrospinning voltage is 18 kV.

[0212] In the finally prepared metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 80 nm, and the particle size of the metal oxide colloidal nanocrystals is 1 / 2 of the fiber diameter; The coloring time of the metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 7.2 s, the fading time is 2.5 s, the optical modulation range at 633 nm is 30%, and the coloring efficiency is 40 C / cm 2 ; After 3000 cycles, the optical modulation range of the metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 85% of the initial optical modulation range.

[0213] The metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

[0214] Example 6

[0215] A preparation method of a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the specific steps are as follows:

[0216] (1) Preparation of raw materials:

[0217] Metal precursor: Sodium metavanadate and vanadium chloride with a mass ratio of 1:1;

[0218] Polymer: Polyacrylonitrile;

[0219] Acidic regulator: A mixed solution of hydrochloric acid and acetic acid with a volume ratio of 1:1, and the concentration of the mixed solution is 0.15 mol / L;

[0220] Growth template agent: Isobutanol;

[0221] Solvent: Deionized water;

[0222] (2) The preparation steps of the metal oxide colloidal nanocrystals are as follows:

[0223] (2.1) Add the metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution with a concentration of 0.2 mol / L, and dropwise add the acidic regulator to the metal ion solution at a rate of 0.26 mL / min;

[0224] Among them, the molar ratio of metal ions to hydrogen ions in the acidic regulator in step (2.1) is 1:2;

[0225] (2.2) Under stirring conditions, dropwise add the growth template agent to the system in step (2.1) at a rate of 2 mL / min. After the addition is completed, continue to stir for 2.5 h until clear, transfer to a hydrothermal reaction kettle with a PTFT inner core, and react at 110 °C for 4.25 h;

[0226] Among them, the molar ratio of metal ions in step (2.1) to the growth template agent in step (2.2) is 1:6;

[0227] (2.3) After the reaction in step (2.2) is completed, cool and centrifuge and wash with deionized water until the pH of the supernatant is 7. Then continue to add deionized water, and continuously collect the upper colloidal solution at a rotation speed of 5500 r / min until there is no Tyndall phenomenon in the supernatant;

[0228] (2.4) Transfer the colloidal solution collected in step (2.3) to a dialysis bag with a molecular weight cut-off of 5000 and dialyze for 7 days;

[0229] (2.5) Freeze-dry and collect the dialysis colloidal solution to obtain metal oxide colloidal nanocrystals with an average particle size of 45 nm;

[0230] The metal oxide colloidal nanocrystals have an organic-inorganic hybrid structure. The surface of the metal oxide colloidal nanocrystals is provided with oxygen-containing organic functional group ligands, and the oxygen-containing organic functional group ligands are isobutoxy groups, hydroxyl groups and metal-O-carbon bonds. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal metal oxide is 6:1;

[0231] (3)Preparation of the spinning solution:

[0232] The polymer is added to the solvent and stirred at a temperature of 40 °C for 5 h to obtain a polymer solution. Then, the metal oxide colloidal nanocrystals are added to the same solvent and stirred at a temperature of 42 °C for 5 h to prepare a metal oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the metal oxide colloidal nanocrystal dispersion are stirred at room temperature and ultrasonically treated for 5 h to obtain the spinning solution;

[0233] The mass fraction of the polymer in the spinning solution is 20%, and the mass ratio of the metal oxide colloidal nanocrystals to the polymer is 3:1;

[0234] (4)The spinning solution in step (3) is electrospun to obtain a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane;

[0235] The process parameters are as follows: the needle gauge used for electrospinning is 22 G, a roller is used as the receiving device, the receiving distance is 15 cm, the horizontal reciprocating distance of the needle is 120 mm, the moving speed is 0.5 cm / s, and the electrospinning voltage is 20 kV.

[0236] In the finally obtained metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 135 nm, and the particle size of the metal oxide colloidal nanocrystals is 1 / 3 of the fiber diameter; the coloring time of the metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane is 7.5 s, the fading time is 2.8 s, the optical modulation range at 633 nm is 35%, and the coloring efficiency is 38 C / cm 2 ; Through 3000 cycles, the optical modulation range of the metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane decays to 87% of the initial optical modulation range.

[0237] The metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane is applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

Claims

1. A method for preparing a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane, characterized in that: Prepare a mixed solution of a polymer and metal oxide colloidal nanocrystals as a spinning solution, and prepare a metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane by electrospinning. The metal oxide colloidal nanocrystals have an organic-inorganic hybrid structure, and the surface of the metal oxide colloidal nanocrystals is provided with oxygen-containing organic functional group ligands. The oxygen-containing organic functional group ligands are alkoxy groups, hydroxyl groups, and metal-O-carbon bonds. The alkoxy groups are 2-hydroxy-propoxy, isopropoxy, hydroxy-ethoxy, 3-hydroxy-propoxy, butoxy, or isobutoxy. The mass ratio of the surface oxygen-containing organic functional group ligands to the internal metal oxide is 4-8:

1. The particle size of the metal oxide colloidal nanocrystals is 6-40 nm; in the metal oxide colloidal nanocrystal-based electrochromic nanofiber membrane, the fiber diameter is 30-200 nm, and the particle size of the metal oxide colloidal nanocrystals is 1 / 5-1 / 2 of the fiber diameter. The preparation steps of the metal oxide colloidal nanocrystals are as follows: (1) Add a metal precursor to deionized water, stir at room temperature until clear to obtain a metal ion solution, and dropwise add an acidic regulator to the metal ion solution at a rate of 0.2-0.3 mL / min. (2) Under stirring conditions, dropwise add a growth template agent to the system in step (1) at a rate of 1-2 mL / min. After the addition is completed, continue stirring for 0.5-3 h until clear, transfer to a hydrothermal reaction kettle with a PTFT inner core, and react at 90-120 °C for 3.5-5 h; the growth template agent is a short-chain alcohol molecule with 2-4 carbon atoms. (3) After the reaction in step (2) is completed, cool and centrifugally wash with deionized water until the pH of the supernatant is 6.5-7. Then continue to add deionized water, and continuously collect the upper colloidal solution at a rotation speed of 4000-7000 r / min until there is no Tyndall phenomenon in the supernatant. (4) Transfer the colloidal solution collected in step (3) to a dialysis bag with a molecular weight cut-off of 3000-5000, and dialyze for 5-7 days. (5) Collect the metal oxide colloidal nanocrystals by freeze-drying the dialyzed colloidal solution.

2. The preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane according to claim 1, characterized in that, The polymer is polyvinylidene fluoride, polyethylene oxide, polymethyl methacrylate, polypropylene, polyamide, or polyacrylonitrile. The mass fraction of the polymer in the spinning solution is 5-20%, and the mass ratio of the metal oxide colloidal nanocrystals to the polymer is 1:3-3:

1.

3. The preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane according to claim 2, wherein, The preparation process of the spinning solution is as follows: Add the polymer to a solvent, stir at a temperature of 30-50 °C for 4-6 h to obtain a polymer solution, then add the metal oxide colloidal nanocrystals to the same solvent, and stir at a temperature of 30-50 °C for 4-6 h to prepare a metal oxide colloidal nanocrystal dispersion with the same mass fraction. The polymer solution and the metal oxide colloidal nanocrystal dispersion are stirred at room temperature and ultrasonically treated for 0.5-5 h to obtain a spinning solution.

4. The preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane according to claim 1, characterized in that, In step (1), the metal precursor is one or more of sodium tungstate, ammonium metatungstate, ammonium tungstate, tetrabutyl titanate, titanium tetrachloride, ammonium vanadate, sodium vanadate, and vanadium chloride.

5. The preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane according to claim 1, characterized in that, In step (1), the acidic regulator is one or more of hydrochloric acid, nitric acid, oxalic acid, and acetic acid.

6. The preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane according to claim 1, characterized in that, In step (1), the concentration of the metal ion solution is 0.2 - 0.6 mol / L, the molar ratio of the metal ion to the hydrogen ion in the acidic regulator is 1:1 - 2; in step (1), the molar ratio of the metal ion to the growth template agent in step (2) is 1:2 - 6.

7. The preparation method of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane according to claim 1, characterized in that, The needle gauge used for electrospinning is 20 - 22G. A roller is used as the receiving device, the receiving distance is 10 - 15 cm, the transverse reciprocating distance of the needle is 80 - 120 mm, the moving speed is 0.3 - 0.5 cm / s, and the electrospinning voltage is 16 - 20 kV.

8. Application of a metal oxide colloid nanocrystal-based electrochromic nanofiber membrane prepared by the method according to any one of claims 1 to 7, characterized in that: Applied to wearable devices, smart displays, electronic tags, and smart windows and window films.

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