Preparation method of nanocrystal-conductive polymer superlattice

Abstract

The application discloses a preparation method of nanocrystal@conductive polymer superlattice, and single-dispersed oleic acid-coated metal oxide nanocrystals are obtained through a thermal decomposition method; a polymerizable ligand exchange strategy is adopted to obtain oleic acid / polymerizable ligand co-coated colloidal nanocrystals; then solvent evaporation-induced assembly is carried out to obtain double-ligand co-coated nanocrystal superlattice; finally, an in-situ oxidation polymerization strategy is adopted to obtain nanocrystal@conductive polymer superlattice. The method has certain universality, and the doping level and type of the nanocrystal@conductive polymer superlattice can be controlled by changing the content and type of polymerizable monomers. Based on the characteristics of the nanocrystal@conductive polymer superlattice material, such as three-dimensional cross-linked polymer conductive network structure and highly ordered and densely packed active center, the application has wide application prospects in the fields of electrochemical energy storage and electrocatalysis.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials technology, specifically relating to a method for preparing nanocrystalline@conductive polymer superlattice. Background Technology

[0002] Nanocrystalline superlattices not only retain the intrinsic properties of nanocrystalline building blocks but also possess unique collective properties due to the coupling effect generated within the assembly, making them valuable for applications in energy storage, catalysis, and optoelectronic devices. Currently, research on nanocrystalline superlattices is moving from "ordered assembly" to "functional applications," aiming to improve the overall performance of the superlattice by integrating the superior properties of each building block. However, as a crucial component of nanocrystalline superlattices, organic ligand molecules on the nanocrystal surface (such as oleic acid and oleylamine), while driving ordered assembly, also form significant physical and energy barriers between nanocrystals. These barriers severely hinder the efficient migration of electrons, holes, or ions within the superlattice, resulting in low mechanical strength and poor conductivity, thus limiting their high-performance and electrochemical applications.

[0003] While ligand exchange and ligand transformation can improve charge transport between nanocrystals to some extent, the resulting superlattices often suffer from reduced order and poor structural stability. In recent years, polymer-grafted nanocrystals, due to the tunable properties and good stability of their surface polymers, have frequently been used as building blocks to prepare nanocrystalline superlattices to enhance their mechanical strength. However, although polymer-grafted nanocrystals with lower molecular weights can assemble into highly ordered superlattices, their mechanical properties are poor. As the polymer molecular weight increases, the entanglement between polymer chains makes it difficult to achieve long-range ordered structures in the superlattice. Furthermore, the polymers on the nanocrystal surface exist in a manner similar to traditional oleic acid or oleylamine, lacking chemical bonding, making it difficult to further improve the structural stability of the nanocrystalline superlattice. The insulating properties of the polymer still hinder the electronic coupling effect between nanocrystals, reducing the conductivity of the superlattice. Therefore, to date, preparing nanocrystalline superlattices with good conductivity and structural stability using precise and controllable methods remains challenging. Summary of the Invention

[0004] This invention addresses a common problem in the fields of nanocrystal self-assembly and superlattice functionalization: how to simultaneously achieve long-range order, macroscopic stability, and efficient charge transport in structures. It proposes an innovative solution. The core of this invention lies in constructing a novel nanocrystal@conductive polymer superlattice through a strategy combining nanocrystal functionalization based on polymerizable ligand coating with in-situ polymerization under superlattice constraints. This invention aims to enhance the mechanical properties of the superlattice and significantly improve its intrinsic conductivity, laying a research foundation for the rational design and construction of novel highly coupled superlattices and their derivatives.

[0005] To achieve the above objectives, in one aspect, the present invention provides a method for preparing nanocrystalline@conductive polymer superlattice, comprising the following steps: (1) Sodium oleate and metal chloride were heated under reflux in a mixed solvent of water and organic solvent, and the oleate precursor was obtained by extraction and separation; (2) Dissolve the oleate precursor in an organic solvent, then add oleic acid as a ligand, and use a high-temperature pyrolysis method to obtain oleic acid-coated monodisperse metal oxide nanocrystals. Disperse the obtained metal oxide nanocrystals in a nonpolar solvent. (3) Add antisolvent to the above metal oxide nanocrystals, wash twice, centrifuge and disperse in a good solvent, add polymerizable ligand molecules to it, and sonicate to obtain a nanocrystal solution coated with dual ligands. (4) Place the nanocrystal solution coated with the dual ligands in an open environment until the solvent evaporates completely to obtain a colloidal nanocrystal superlattice template. Add an oxidant solution containing inorganic acid to the colloidal nanocrystal superlattice template to carry out oxidative polymerization and obtain a nanocrystal@conductive polymer superlattice with a long-range ordered structure.

[0006] In some embodiments, in step (1), the metal chloride is a transition metal chloride, specifically one or more of FeCl3·6H2O, MnCl2·4H2O, CoCl2·6H2O, and NiCl2·6H2O.

[0007] In some implementations, in step (1), the molar ratio is 8:1 to 1:1, preferably 5:1 to 3:1.

[0008] In some implementations, in step (1), the heating reflux is carried out at 60~70°C for 3~4 hours.

[0009] In some embodiments, in step (2), the organic solvent is one or more combinations of octadecene, hexadecene, eicosane, benzyl ether, and diphenyl ether.

[0010] In some embodiments, in step (2), the molar ratio of ligand oleic acid to the oleate precursor is 8:5 to 3:5, preferably 6:5 to 4:5.

[0011] In some embodiments, in step (2), the reaction temperature of the high-temperature pyrolysis method is 250~330℃ and the reaction time is 0.5~2 h.

[0012] In some embodiments, in step (2), depending on the metal chloride added in step (1), the type of oleic acid-coated monodisperse metal oxide nanocrystals obtained in step (2) is different. For example, they can be Fe3O4, MnFe2O4, CoFe2O4, or NiFe2O4 nanocrystals; the particle size of the obtained metal oxide nanocrystals is 5~20 nm.

[0013] In some embodiments, in step (2), the nonpolar solvent is one or more of n-hexane, hexane, octane, and cyclohexane.

[0014] In some embodiments, in step (3), the antisolvent is one or more of methanol, ethanol, propanol, isopropanol, and butanol; and the benign solvent is one or more of chloroform, toluene, cyclohexane, and tetrahydrofuran.

[0015] In some embodiments, in step (3), the polymerizable ligand molecule is one or more of pyrrole, thiophene, aniline, and 3,4-ethylenedioxythiophene; and the ultrasonic time is 15 to 30 minutes.

[0016] In some embodiments, in step (3), the molar ratio of the polymerizable ligand molecule to the metal oxide nanocrystal is 17:2 to 20:1, preferably 17:2 to 10:1.

[0017] In some embodiments, in step (4), the inorganic acid is any one of hydrochloric acid, sulfuric acid or phosphoric acid; the concentration of the inorganic acid in the oxidant solution containing the inorganic acid is 0.01 ~ 0.1 mol / L.

[0018] In some embodiments, in step (4), the oxidant is selected from one of ammonium persulfate, ferric chloride, and p-toluenesulfonic acid.

[0019] In some embodiments, in step (4), the volume ratio of the oxidant solution containing inorganic acid to the nanocrystal solution coated with dual ligands is 6:1 to 2:1, preferably 4:1 to 3:1.

[0020] In some embodiments, in step (4), the oxidative polymerization is carried out at 25-60°C for 6-72 h.

[0021] In another aspect, the present invention provides nanocrystalline@conductive polymer superlattice obtained by the above preparation method.

[0022] In another aspect, the present invention provides the application of the nanocrystals@conductive polymer superlattice in energy storage and photoelectrocatalysis.

[0023] This invention starts with oleic acid ligand-coated nanocrystals, introducing conductive polymer monomers as polymerizable ligands onto the nanocrystal surface. A solvent evaporation-induced strategy is used to regulate intergranular van der Waals forces, inducing the ordered assembly of nanocrystals to construct a nanocrystal superlattice template. An in-situ polymerization strategy is then employed to form a three-dimensional cross-linked conductive polymer network structure within the superlattice, thereby obtaining a nanocrystal@conductive polymer superlattice while simultaneously improving its mechanical stability and conductivity. This method for constructing nanocrystal@conductive polymer superlattices has a certain degree of universality. The content and type of polymerizable ligands can be adjusted (e.g., pyrrole, thiophene, aniline, etc.), and the types of nanocrystals are diverse (Fe3O4, MnFe2O4, CoFe2O4, etc.), thus allowing for the acquisition of nanocrystal@conductive polymer superlattices with different compositions. The nanocrystal@conductive polymer superlattice synthesized in this invention possesses a three-dimensional cross-linked polymer conductive network structure and highly ordered, densely packed active centers, making it widely applicable in fields such as energy storage and conversion.

[0024] This invention utilizes a process of "introducing polymerizable ligands, regulating self-assembly behavior, and in-situ oxidative polymerization" to induce the ordered self-assembly of nanocrystals into a superlattice structure by regulating the synergistic effects between ligand molecules. Further, in-situ oxidative polymerization is used to crosslink the polymerizable ligands, thus preparing a nanocrystal@conductive polymer superlattice. Starting with ligands on the nanocrystal surface, this invention designs novel superlattice structures at the molecular level and regulates electronic coupling effects. By constructing a conductive polymer network, it enhances the mechanical stability and electrochemical performance of the nanocrystal superlattice.

[0025] The method of this invention is simple, highly flexible, and universal. By introducing conductive polymer monomers as polymerizable ligands onto the surface of nanocrystals, the prepared nanocrystal@conductive polymer superlattice achieves improved electrochemical performance and shows good application prospects in electrochemical energy storage. Attached Figure Description

[0026] Figure 1 These are scanning electron microscope (SEM) images of the oleic acid / pyrrole-coated Fe3O4 nanocrystals before and after polymerization of the superlattice, prepared in Example 1 of this invention. Figure 2 This is a scanning electron microscope image of the oleic acid / pyrrole-coated Fe3O4 nanocrystal assembly prepared in Comparative Example 1 of this invention. Figure 3 This is a scanning electron microscope image of Fe3O4 nanocrystals@polypyrrole superlattice polymerized for 86 h, prepared in Comparative Example 2 of this invention. Figure 4 This is a scanning electron microscope image of the Fe3O4 nanocrystals@polyaniline superlattice prepared in Example 2 of the present invention; Figure 5 This is a scanning electron microscope image of the CoFe2O4 nanocrystals@polythiophene superlattice prepared in Example 3 of the present invention; Figure 6 This is a scanning electron microscope image of the MnFe2O4 nanocrystals@polyaniline superlattice prepared in Example 4 of the present invention; Figure 7 Transmission electron microscopy (TEM) image and elemental scanning electron microscope (ESS) image of the Fe3O4 nanocrystals@polyaniline superlattice prepared in Example 2 of this invention; Figure 8 X-ray diffraction analysis of Fe3O4 nanocrystals@polyaniline superlattice prepared in Example 2 of this invention; Figure 9 Thermogravimetric analysis of Fe3O4 nanocrystals@polyaniline superlattice prepared in Example 2 of this invention; Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0028] Example 1: (1) Preparation of ferric oleate precursor: 18.24 g sodium oleate, 5.4 g ferric chloride hexahydrate, 30 mL water, 40 mL ethanol and 80 mL n-hexane were mixed evenly and refluxed at 60 °C for 4 h; waxy ferric oleate was obtained by extraction and vacuum drying. (2) Preparation of Fe3O4 nanocrystals coated with oleic acid: 9 g of ferric oleate, 2.5 g of oleic acid and 50 g of octadecene were mixed evenly, heated to 120°C, and vacuumed for 0.5 h. Then nitrogen gas was introduced and the temperature was raised to 320°C in a nitrogen atmosphere for 1 h. An appropriate amount of ethanol and isopropanol were added to the reaction solution and centrifuged at 5000 rpm for 5 min. The precipitate was dispersed in n-hexane to obtain a stable colloidal solution of Fe3O4 nanocrystals coated with oleic acid. The concentration of Fe3O4 nanocrystals coated with oleic acid was about 40 mg / mL.

[0029] (3) Preparation of Fe3O4 nanocrystals co-coated with oleic acid / pyrrole: excess oleic acid and free oleic acid on the surface of the nanocrystals were removed by washing with methanol and isopropanol; the washed nanocrystals were then redispersed in CHCl3, and 0.5 mL of pyrrole monomer was added dropwise to the solution and sonicated for 20 min to obtain a colloidal solution of Fe3O4 nanocrystals co-coated with oleic acid / pyrrole.

[0030] (4) Preparation of Fe3O4 nanocrystals@polypyrrole superlattice: The colloidal solution of Fe3O4 nanocrystals co-coated with oleic acid / pyrrole prepared in the above steps was transferred to an open container until the solvent evaporated completely, thus obtaining the Fe3O4 nanocrystal superlattice template co-coated with oleic acid / pyrrole. 10 mL of polymerization solution (composed of 0.05 mol / L HCl and 10 mg / mL ferric chloride) was added to the nanocrystal superlattice template, and oxidative polymerization was carried out for 12 h. Finally, the polymerization solution was removed, and the sample was washed several times with deionized water and dried in an oven to obtain the Fe3O4 nanocrystals@polypyrrole superlattice.

[0031] Example 2: (1) Preparation of ferric oleate precursor: 18.24 g sodium oleate, 5.4 g ferric chloride hexahydrate, 30 mL water, 40 mL ethanol and 80 mL n-hexane were mixed evenly and refluxed at 60 °C for 4 h; waxy ferric oleate was obtained by extraction and vacuum drying. (2) Preparation of Fe3O4 nanocrystals coated with oleic acid: 9 g of ferric oleate, 3.7 g of oleic acid and 50 g of octadecene were mixed evenly, heated to 120°C, and vacuumed for 0.5 h. Then nitrogen gas was introduced and the temperature was raised to 320°C in a nitrogen atmosphere for 1 h. Appropriate amounts of ethanol and isopropanol were added to the reaction solution and centrifuged at 5000 rpm for 5 min. The precipitate was dispersed in n-hexane to obtain a stable colloidal solution of Fe3O4 nanocrystals coated with oleic acid. The concentration of Fe3O4 nanocrystals coated with oleic acid was about 40 mg / mL.

[0032] (3) Preparation of Fe3O4 nanocrystals co-coated with oleic acid / aniline: excess oleic acid and free oleic acid on the surface of the nanocrystals were removed by washing with methanol and isopropanol; the washed nanocrystals were then redispersed in CHCl3, and 0.8 mL of aniline monomer was added dropwise to the solution and sonicated for 30 min to obtain a colloidal solution of Fe3O4 nanocrystals co-coated with oleic acid / aniline.

[0033] (4) Preparation of Fe3O4 nanocrystals@polyaniline superlattice: The colloidal solution of Fe3O4 nanocrystals co-coated with oleic acid / aniline prepared in the above steps was transferred to an open container until the solvent evaporated completely, thus obtaining the Fe3O4 nanocrystal superlattice template co-coated with oleic acid / aniline. 10 mL of polymerization solution (composed of 0.05 mol / L HCl and 20 mg / mL ammonium persulfate) was added to the Fe3O4 nanocrystal superlattice template co-coated with oleic acid / aniline, and oxidative polymerization was carried out for 24 h. Finally, the polymerization solution was removed, and the sample was washed several times with deionized water and dried in an oven to obtain the Fe3O4 nanocrystals@polyaniline superlattice.

[0034] Example 3: (1) Preparation of cobalt iron oleate precursor: 9.784 g sodium oleate, 2.2 g ferric chloride hexahydrate, 0.9 g cobalt chloride tetrahydrate, 20 mL water, 20 mL ethanol and 40 mL n-hexane were mixed evenly and refluxed at 60℃ for 4 h; waxy manganese iron oleate was obtained by extraction, vacuum drying and other treatments. (2) Preparation of oleic acid-coated CoFe2O4 nanocrystals: 4.5 g cobalt iron oleate, 1.1 g oleic acid and 19 g octadecene were mixed evenly, heated to 110℃, vacuumed for 1 h, and then nitrogen gas was introduced. The mixture was heated to 320℃ in a nitrogen atmosphere and reacted for 2 h. An appropriate amount of ethanol and isopropanol were added to the reaction solution and centrifuged at 6000 rpm for 5 min. The precipitate was dispersed in n-hexane to obtain a stable colloidal solution of oleic acid-coated CoFe2O4 nanocrystals, wherein the concentration of oleic acid-coated CoFe2O4 nanocrystals was about 30 mg / mL.

[0035] (3) Preparation of CoFe2O4 nanocrystals co-coated with oleic acid / thiophene: excess oleic acid and free oleic acid on the surface of the nanocrystals were removed by washing with methanol and isopropanol; the washed nanocrystals were then redispersed in CHCl3, and 0.4 mL of thiophene monomer was added dropwise to the solution and sonicated for 30 min to obtain a colloidal solution of CoFe2O4 nanocrystals co-coated with oleic acid / thiophene.

[0036] (4) Preparation of CoFe2O4 nanocrystals@polythiophene superlattice: The oleic acid / thiophene co-coated CoFe2O4 nanocrystal colloidal solution prepared in the above steps was transferred to an open container until the solvent evaporated completely, resulting in an oleic acid / thiophene co-coated CoFe2O4 nanocrystal superlattice template. 10 mL of polymerization solution (composed of 0.08 mol / L HCl and 20 mg / mL ammonium persulfate) was added to the nanocrystal superlattice template, and polymerization was carried out at 40 °C for 12 h. Finally, the polymerization solution was removed, and the sample was washed several times with deionized water and dried in an oven to obtain the CoFe2O4 nanocrystals@polythiophene superlattice.

[0037] Example 4: (1) Preparation of manganese ferric oleate precursor: 19.48 g sodium oleate, 4.3 g ferric chloride hexahydrate, 1.6 g manganese chloride tetrahydrate, 40 mL water, 40 mL ethanol and 80 mL n-hexane were mixed evenly and refluxed at 60℃ for 4 h; waxy manganese ferric oleate was obtained by extraction, vacuum drying and other treatments. (2) Preparation of oleic acid-coated MnFe2O4 nanocrystals: 9 g manganese iron oleate, 2.125 g oleic acid and 37.5 g octadecene were mixed evenly, heated to 110℃, vacuumed for 1 h, and then nitrogen gas was introduced. The mixture was heated to 320℃ in a nitrogen atmosphere and reacted for 2 h. An appropriate amount of ethanol and isopropanol were added to the reaction solution and centrifuged at 4000 rpm for 3 min. The precipitate was dispersed in n-hexane to obtain a stable colloidal solution of oleic acid-coated MnFe2O4 nanocrystals, wherein the concentration of oleic acid-coated MnFe2O4 nanocrystals was about 30 mg / mL.

[0038] (3) Preparation of MnFe2O4 nanocrystals co-coated with oleic acid / aniline: excess oleic acid and free oleic acid on the surface of the nanocrystals were removed by washing with methanol and isopropanol; the washed nanocrystals were then redispersed in tetrahydrofuran, and 1 mL of aniline monomer was added dropwise to the solution and sonicated for 30 min to obtain a colloidal solution of MnFe2O4 nanocrystals co-coated with oleic acid / aniline.

[0039] (4) Preparation of MnFe2O4 nanocrystals@polyaniline superlattice: The colloidal solution of MnFe2O4 nanocrystals co-coated with oleic acid / aniline prepared in the above steps was transferred to an open container until the solvent evaporated completely, thus obtaining an oleic acid / aniline co-coated MnFe2O4 nanocrystal superlattice template. 10 mL of polymerization solution (composed of 0.05 mol / L HCl and 20 mg / mL ammonium persulfate) was added to the nanocrystal superlattice template, and oxidative polymerization was carried out for 48 h. Finally, the polymerization solution was removed, and the sample was washed multiple times with deionized water and dried in an oven to obtain the MnFe2O4 nanocrystals@polyaniline superlattice.

[0040] Comparative Example 1 In this comparative example, the amount of pyrrole used in the synthesis of the oleic acid / pyrrole co-coated nanocrystalline system was 2 mL, and the other parameters were the same as in Example 1.

[0041] Comparative Example 2 In this comparative example, the polymerization time in the Fe3O4 nanocrystals@polypyrrole superlattice system synthesis process was 86 h, and the remaining steps were the same as in Example 1.

[0042] The structure of the nanocrystalline@conductive polymer superlattice in this invention is characterized below by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction.

[0043] Scanning electron microscopy analysis Figure 1The images show scanning electron microscope (SEM) images of the oleic acid / pyrrole-coated Fe3O4 nanocrystal superlattice before and after polymerization in Example 1. As can be seen from the images, the introduction of polymerizable ligands into the nanocrystal surface did not alter the self-assembly behavior of the nanocrystals; the nanocrystals co-coated with oleic acid and pyrrole could assemble into an ordered nanocrystal superlattice. Furthermore, after in-situ polymerization and oxidation for an appropriate time, the ordered structure of the nanocrystal superlattice remained intact. However, in Comparative Example 1, when there were too many polymerizable ligand molecules, the number of free polymerizable ligand molecules in the solution increased, altering the thermodynamic equilibrium of volatile assembly driven by the long-chain ligand oleic acid, leading to disordered stacking of the nanocrystals, such as... Figure 2 In Comparative Example 2, if the polymerization time is too long, the nanocrystals will be extensively etched by HCl, and the nanocrystal superlattice structure will collapse, such as... Figure 3 These results demonstrate that the control of the content of polymerizable ligand molecules (molar ratio of polymerizable ligand to nanocrystals 17:2~20:1) and polymerization conditions (25~60℃, 6~72 h) plays a crucial role in the formation of nanocrystals@conductive polymer superlattices. Figure 4-6 The images shown are scanning electron microscope (SEM) images of the nanocrystals@conductive polymer superlattices prepared in Examples 2, 3, and 4, respectively. Their structures all maintain a highly ordered three-dimensional continuity, demonstrating the general applicability of the method of the present invention.

[0044] Transmission electron microscopy and elemental scanning analysis Figure 7 The images show the transmission electron microscope (TEM) image and elemental distribution map of the Fe3O4@polyaniline superlattice prepared in Example 2 of this invention. As can be seen from the figures, the superlattice maintains good structural order, and a coating layer exists on the surface of the nanocrystals. Elemental scanning analysis revealed the presence of four elements—Fe, C, O, and N—on the superlattice surface, with a consistent distribution trend, all present in the superlattice region. This demonstrates that a polyaniline coating layer was successfully formed on the nanocrystal surface.

[0045] X-ray diffraction analysis Figure 8 The X-ray diffraction pattern of the Fe3O4@polyaniline superlattice prepared in Example 2 of this invention is shown in the figure. As can be seen from the figure, the XRD diffraction peaks of Fe3O4@polyaniline are consistent with the standard card PDF#75-0449 of Fe3O4. From left to right, they belong to the diffraction peaks of the (111), (220), (311), (222), (400), (331), (422), (511), (440), (531), (620), (533), and (622) crystal planes of Fe3O4. The Fe3O4@polyaniline sample shows a broad diffraction peak at around 23°, which is a characteristic diffraction peak of polyaniline, indicating that the aniline ligand molecules have been successfully oxidized and polymerized into polyaniline.

[0046] Thermogravimetric analysis Figure 9The TGA spectrum of the Fe3O4@polyaniline superlattice prepared in Example 2 of this invention is shown in the figure. It can be seen from the figure that the weight loss rate of the Fe3O4@polyaniline sample is about 7.26%, and the weight loss temperature range is 300℃-400℃. The sample has a low weight loss rate and a high weight loss temperature, indicating the presence of polyaniline.

Claims

1. A method for preparing nanocrystalline@conductive polymer superlattice, comprising the following steps: (1) Sodium oleate and metal chloride were heated under reflux in a mixed solvent of water and organic solvent, and the oleate precursor was obtained by extraction and separation; (2) Dissolve the oleate precursor in an organic solvent, then add oleic acid as a ligand, and use a high-temperature pyrolysis method to obtain oleic acid-coated monodisperse metal oxide nanocrystals. Disperse the obtained metal oxide nanocrystals in a nonpolar solvent. (3) Add antisolvent to the above metal oxide nanocrystals, wash twice, centrifuge and disperse in a good solvent, add polymerizable ligand molecules to it, and sonicate to obtain a nanocrystal solution coated with dual ligands. (4) Place the nanocrystal solution coated with the dual ligands in an open environment until the solvent evaporates completely to obtain a colloidal nanocrystal superlattice template. Add an oxidant solution containing inorganic acid to the colloidal nanocrystal superlattice template to carry out oxidative polymerization and obtain a nanocrystal@conductive polymer superlattice with a long-range ordered structure.

2. The preparation method according to claim 1, wherein, In step (1), the metal chloride is a transition metal chloride selected from one or more of FeCl3·6H2O, MnCl2·4H2O, CoCl2·6H2O, and NiCl2·6H2O.

3. The preparation method according to claim 1, wherein, In step (1), the molar ratio of sodium oleate to metal chloride is 8:1 to 1:

1.

4. The preparation method according to claim 1, wherein, In step (1), the heating reflux is carried out at 60~70℃ for 3~4 h.

5. The preparation method according to claim 1, wherein, In step (2), at least one of the following conditions must be met: The organic solvent is one or more combinations of octadecene, hexadecene, eicosane, benzyl ether, and diphenyl ether; The molar ratio of ligand oleic acid to the oleate precursor is 8:5 to 3:5; The reaction temperature of the high-temperature pyrolysis method is 250~330℃, and the reaction time is 0.5~2 h; The particle size of the obtained metal oxide nanocrystals is 5~20 nm; The nonpolar solvent is one or more of n-hexane, hexane, octane, and cyclohexane.

6. The preparation method according to claim 1, wherein, In step (3), at least one of the following conditions must be met: The antisolvent is one or more selected from methanol, ethanol, propanol, isopropanol, and butanol; The benign solvent is one or more of chloroform, toluene, cyclohexane, and tetrahydrofuran; The polymerizable ligand molecule is one or more of pyrrole, thiophene, aniline, and 3,4-ethylenedioxythiophene; the ultrasonic time is 15-30 min. The molar ratio of the polymerizable ligand molecule to the metal oxide nanocrystal is 17:2 to 20:

1.

7. The preparation method according to claim 1, wherein, In step (4), at least one of the following conditions must be met: The inorganic acid is any one of hydrochloric acid, sulfuric acid, or phosphoric acid; The concentration of the inorganic acid in the oxidant solution containing the inorganic acid is 0.01 ~ 0.1 mol / L; The oxidant is selected from one of ammonium persulfate, ferric chloride, and p-toluenesulfonic acid; The volume ratio of the inorganic acid-containing oxidant solution to the dual-ligand-coated nanocrystal solution is 6:1 to 2:

1. The oxidative polymerization was carried out at 25-60°C for 6-72 h.

8. The nanocrystalline@conductive polymer superlattice obtained by the preparation method according to any one of claims 1-7.

9. The application of the nanocrystalline@conductive polymer superlattice of claim 8 in energy storage and photoelectrocatalysis.

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