A method for preparing axially periodic core-shell nanoheterostructure materials

Abstract

This invention provides a method for preparing axially periodic core-shell heterojunction nanostructures. First, Al-M nanowires with endpoints are obtained using a catalytic growth method. Then, the endpoints A1 of the Al-M nanowires are removed using alkylphosphine to obtain pure colloidal M nanowires. Next, a silver source solution is mixed with a dispersion of the pure colloidal M nanowires for an ion exchange reaction to obtain M@A2 uniform core-shell heterojunction nanowires. Finally, the M@A2 core-shell nanowires are dispersed in a solvent and subjected to heat treatment. The Rayleigh fluid instability in inorganic solids causes deformation, leading to structural evolution of the uniform core-shell heterojunction nanowires and the formation of axially periodic core-shell heterojunctions. Compared with existing technologies, this invention is the first to utilize the principle of Rayleigh fluid instability in inorganic solids to precisely synthesize axially periodic nanostructures with adjustable size and periodicity, opening a new avenue for the design and synthesis of axially periodic nanostructures.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials, and in particular to a method for preparing an axially periodic core-shell nanoheterostructure material. Background Technology

[0002] One-dimensional nanoheterostructures are widely used in electronics, optoelectronics, energy, environment, and biomedicine due to their advantages such as tunable band structure, strong carrier-carrier interactions, large optical absorption cross-section, long-distance carrier transport, low Auger recombination rate, and strong anisotropy. Among these, axially periodic core-shell heterostructures have attracted increasing attention due to their unique anisotropic and periodic structure, inherently high surface area, abundant transport channels, and multi-scale surface roughness, as reported in the journal *Advanced Materials* (2022, Vol. 34, p. 2200776). These properties endow them with unique electrical, optical, and catalytic properties. However, the precise synthesis and control of axially periodic core-shell heterostructures remains a significant challenge.

[0003] The British journal *Nanotechnology* (2006, Vol. 17, p. 5954) reported a Rayleigh fluid instability in a low-melting-point metal, resulting in axially periodic Au nanowires. The *Journal of the American Chemical Society* (2008, Vol. 130, p. 5651) reported the fabrication of necklace-like Cu@PVA axially periodic nanoheterostructures based on Rayleigh fluid instability in polymers. *Nature Nanotechnology* (2015, Vol. 10, p. 345) reported a crystal growth method based on Rayleigh fluid instability of surface-diffused atoms, successfully synthesizing Ge and Si axially periodic heterowires with tunable diameter and periodicity.

[0004] However, no method has been reported for synthesizing axially periodic core-shell structures based on Rayleigh fluid instability in inorganic solids. Due to the stability of solid lattices, the precise fabrication of axially periodic core-shell heterostructures in inorganic solids using Rayleigh fluid instability is extremely challenging. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing axially periodic core-shell nanoheterostructures. The method provided by the present invention is the first to accurately synthesize axially periodic nanoheterostructures based on the principle of Rayleigh fluid instability in inorganic solids, and the products exhibit uniform morphology and size.

[0006] This invention provides a method for preparing axially periodic core-shell nanoheterojunction materials, comprising the following steps:

[0007] A) Al-M nanowires were prepared by catalytic growth method, and then the endpoints A1 of the Al-M nanowires were removed by alkylphosphine to obtain pure colloidal M nanowires.

[0008] In the Al-M nanowires, Al is an inorganic compound of Ag; M is at least one of sulfide and selenide.

[0009] B) The silver source solution was mixed with the dispersion of the pure colloidal M nanowires to carry out an ion exchange reaction to obtain M@A2 core-shell nanowires;

[0010] in:

[0011] The silver source solution is a solution obtained by dissolving a silver source in a solvent;

[0012] The dispersion of the pure colloidal M nanowires is a dispersion obtained by dispersing the pure colloidal M nanowires in a solvent.

[0013] In the M@A2 core-shell nanowire, M is the core nanowire, and A2 is the shell layer covering the surface of the core nanowire; A2 is an inorganic compound of Ag.

[0014] C) The M@A2 core-shell nanowires are dispersed in a solvent and then heat-treated to obtain an axially periodic core-shell nanoheterojunction material.

[0015] Preferably, in step B), the temperature of the ion exchange reaction is 10–40°C and the time is 5–60 min.

[0016] Preferably, in step C), the heat treatment temperature is 40–120°C and the time is 3–24 hours.

[0017] Preferably, in step B), the silver source is at least one of silver diethyldithiocarbamate, silver acetate, and silver nitrate.

[0018] Preferably, in step B), the molar ratio of silver ions in the silver source solution to metal cations in the dispersion of pure colloidal M nanowires is 1:(0.1-3).

[0019] Preferably, in step C):

[0020] The solvent is at least one of toluene, n-hexane, and chloroform;

[0021] The ratio of the M@A2 core-shell nanowires to the solvent is 1 mg:(0.5-2) mL.

[0022] Preferably, step A) specifically includes:

[0023] A1) A mixture of silver source, metal source, S / Se source and organic solvent was heated to react and obtain Al-M nanowires;

[0024] A2) Mix alkyl phosphorus with a solvent to obtain an alkyl phosphorus solution;

[0025] A3) The Al-M nanowires are mixed with a solvent to obtain an Al-M nanowire dispersion;

[0026] A4) The alkylphosphine solution was mixed and reacted with the A1-M nanowire dispersion to obtain pure colloidal M nanowires;

[0027] There is no order restriction between steps A1) and A2), and there is no order restriction between steps A2) and A3).

[0028] Preferably, in step A1), the reaction temperature is 185–280°C and the time is 30–90 min; in step A2), the alkylphosphine is tri-n-octylphosphine and / or tributylphosphine.

[0029] In step A4), the reaction temperature is 15–40°C and the time is 3–6 h.

[0030] Preferably, in the A1-M nanowire, the diameter of the endpoint A1 is 4–20 nm;

[0031] The diameter of the Al-M nanowires is 4–20 nm;

[0032] The length of the Al-M nanowires is 20–3000 nm.

[0033] Preferably, the M@A2 core-shell nanowires obtained in step B) include Co9S8@Ag2S core-shell nanowires, ZnS@Ag2S core-shell nanowires, or ZnSe@Ag2Se core-shell nanowires;

[0034] The axially periodic core-shell nanoheterojunction materials obtained in step C) include -[Co9S8@Ag2S]-Co9S8-axially periodic core-shell nanoheterojunction, -[ZnS@Ag2S]-ZnS-axially periodic core-shell nanoheterojunction, or -[ZnSe@Ag2Se]-ZnSe-axially periodic core-shell nanoheterojunction.

[0035] The preparation method provided by this invention first uses a catalytic growth method to obtain A1-M nanowires with endpoints, and then removes the endpoints A1 of the A1-M nanowires with alkylphosphine to obtain pure colloidal M nanowires. Next, a silver source solution is mixed with a dispersion of the pure colloidal M nanowires for an ion exchange reaction to obtain M@A2 uniform core-shell heterojunction nanowires. Finally, the M@A2 core-shell nanowires are dispersed in a solvent and subjected to heat treatment. The Rayleigh fluid instability in inorganic solids causes deformation, leading to structural evolution of the uniform core-shell heterojunction nanowires to obtain axially periodic core-shell heterojunctions. Compared with existing technologies, this invention, for the first time, utilizes the principle of Rayleigh fluid instability in inorganic solids to precisely synthesize axially periodic nanoheterostructures with adjustable size and periodicity, opening a new avenue for the design and synthesis of axially periodic nanoheterostructures. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of Al-M nanowires in step A) of the preparation method of the present invention;

[0038] Figure 2 This is a schematic diagram illustrating the structural evolution of the products in each step of the preparation method of the present invention;

[0039] Figure 3 This is a transmission electron microscope image of the Co9S8 nanowires obtained in step A) of Example 1;

[0040] Figure 4 This is a transmission electron microscope image of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1.

[0041] Figure 5 The image shows the EDS elemental surface analysis of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1.

[0042] Figure 6 The image shows the EDS line scan of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1.

[0043] Figure 7 The EDS spectrum of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1 is shown below.

[0044] Figure 8 The image is a transmission electron microscope image of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1.

[0045] Figure 9 Dark-field transmission electron microscopy image of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1;

[0046] Figure 10 The image shows the EDS elemental surface analysis of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1.

[0047] Figure 11 EDS line scan of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1;

[0048] Figure 12 The EDS spectrum of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1 is shown below.

[0049] Figure 13 The X-ray diffraction pattern of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1;

[0050] Figure 14 This is a high-resolution transmission electron microscope image of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1.

[0051] Figure 15 This is a transmission electron microscope image of the ZnS nanowires obtained in step A) of Example 2;

[0052] Figure 16 This is a transmission electron microscope image of the ZnS@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 2.

[0053] Figure 17 The image shows the EDS elemental surface analysis of the ZnS@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 2.

[0054] Figure 18 The image shows a transmission electron microscope image of the [ZnS@Ag2S]-ZnS-axially periodic core-shell nanoheterostructure obtained in step C) of Example 2.

[0055] Figure 19The image shows the EDS elemental surface analysis of the -[ZnS@Ag2S]-ZnS-axially periodic core-shell nanoheterostructure obtained in step C) of Example 2.

[0056] Figure 20 This is a transmission electron microscope image of the ZnSe nanowires obtained in step A) of Example 3;

[0057] Figure 21 This is a transmission electron microscope image of the ZnSe@Ag2Se core-shell heterojunction nanowires obtained in step B) of Example 3;

[0058] Figure 22 The image shows the EDS elemental surface analysis of the ZnSe@Ag2Se core-shell heterojunction nanowires obtained in step B) of Example 3.

[0059] Figure 23 The image shows a transmission electron microscope image of the [ZnSe@Ag2Se]-ZnSe-axially periodic core-shell nanoheterostructure obtained in step C) of Example 3.

[0060] Figure 24 The image shows the EDS elemental surface analysis of the -[ZnSe@Ag2Se]-ZnSe-axially periodic core-shell nanoheterostructure obtained in step C) of Example 3. Detailed Implementation

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0062] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0063] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0064] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0065] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 5~15℃ / min means that the units for the left endpoint "5" and the right endpoint "15" are both ℃ / min.

[0066] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0067] This invention provides a method for preparing axially periodic core-shell nanoheterojunction materials, comprising the following steps:

[0068] A) Al-M nanowires were prepared by catalytic growth method, and then the endpoints A1 of the Al-M nanowires were removed by alkylphosphine to obtain pure colloidal M nanowires.

[0069] In the Al-M nanowires, Al is an inorganic compound of Ag; M is at least one of sulfide and selenide.

[0070] B) The silver source solution was mixed with the dispersion of the pure colloidal M nanowires to carry out an ion exchange reaction to obtain M@A2 core-shell nanowires;

[0071] in:

[0072] The silver source solution is a solution obtained by dissolving a silver source in a solvent;

[0073] The dispersion of the pure colloidal M nanowires is a dispersion obtained by dispersing the pure colloidal M nanowires in a solvent.

[0074] In the M@A2 core-shell nanowire, M is the core nanowire, and A2 is the shell layer covering the surface of the core nanowire; A2 is an inorganic compound of Ag.

[0075] C) The M@A2 core-shell nanowires are dispersed in a solvent and then heat-treated to obtain an axially periodic core-shell nanoheterojunction material.

[0076] Regarding step A) :

[0077] A) Al-M nanowires were prepared by catalytic growth, and then the endpoints A1 of the Al-M nanowires were removed by alkylphosphine to obtain pure colloidal M nanowires.

[0078] In this invention, the A1-M nanowire is a nanowire with endpoints, and its structure includes endpoints and a nanowire body connected to the endpoints; wherein the endpoints are mostly spherical (but can also be other shapes), the endpoints are A1, and the nanowire body is M. Figure 1 As shown, spherical end 1 is endpoint A1, and 2 is the nanowire body M.

[0079] In this invention, in the Al-M nanowires, Al is an inorganic compound of Ag, preferably Ag₂S or Ag₂Se. M is at least one of sulfides and selenides, preferably at least one of Co₉S₈, ZnS, and ZnSe. In this invention, the Al-M nanowires are preferably Ag₂S-Co₉S₈ nanowires, Ag₂S-ZnS nanowires, or Ag₂Se-ZnSe nanowires.

[0080] In this invention, the diameter of the endpoint A1 in the Al-M nanowire is preferably 4–20 nm. The diameter of the Al-M nanowire is preferably 4–20 nm. The length of the Al-M nanowire is preferably 20–3000 nm.

[0081] In this invention, step A) preferably includes:

[0082] A1) A mixture of silver source, metal source, S / Se source and organic solvent was heated to react and obtain Al-M nanowires;

[0083] A2) Mix alkyl phosphorus with a solvent to obtain an alkyl phosphorus solution;

[0084] A3) The Al-M nanowires are mixed with a solvent to obtain an Al-M nanowire dispersion;

[0085] A4) The alkylphosphine solution was mixed and reacted with the A1-M nanowire dispersion to obtain pure colloidal M nanowires;

[0086] There is no order restriction between steps A1) and A2), and there is no order restriction between steps A2) and A3).

[0087] [Regarding step A1]:

[0088] In this invention, the silver source is preferably a silver salt, more preferably at least one of silver diethyldithiocarbamate, silver acetate and silver nitrate, and most preferably silver diethyldithiocarbamate.

[0089] In this invention, the metal source is preferably a cobalt source or a zinc source. The cobalt source is preferably a cobalt salt, more preferably at least one of cobalt diethyldithiocarbamate, cobalt acetate, and cobalt nitrate, and most preferably cobalt nitrate. The zinc source is preferably a zinc salt, more preferably at least one of zinc diethyldithiocarbamate, zinc acetate, and zinc nitrate, and most preferably zinc diethyldithiocarbamate or zinc acetate.

[0090] In this invention, the S / Se source refers to a sulfur source or a selenium source. The S source (i.e., sulfur source) is preferably octyl mercaptan and / or dodecyl mercaptan, more preferably dodecyl mercaptan. The Se source (i.e., selenium source) is preferably at least one of selenium dioxide, selenium powder, and diphenyldiselenoether, most preferably selenium dioxide.

[0091] In this invention, the organic solvent is preferably at least one of unsaturated organic acid solvent and unsaturated alkene solvent, more preferably oleylamine and / or oleic acid, and most preferably oleic acid.

[0092] For Ag2S-Co9S8 or Ag2S-ZnS nanowires:

[0093] The above steps include: mixing a silver source, a metal source, a sulfur source, and an organic solvent and heating them to react, thereby obtaining Al-M nanowires; wherein the metal source is a cobalt source or a zinc source. The types of silver source, metal source, sulfur source, and organic solvent are the same as described above and will not be repeated here.

[0094] For Ag2Se-ZnSe nanowires:

[0095] There are two preparation methods: (1) The first method: a silver source, a zinc source, a Se source, and an organic solvent are mixed and heated to react, yielding Al-M nanowires. The types of silver source, zinc source, Se source, and organic solvent are the same as described above and will not be repeated here. (2) The second method: Ag2Se, a zinc source, a Se source, and an organic solvent are mixed and heated to react, yielding Al-M nanowires. Ag2Se serves as a catalyst seed; the types of zinc source, Se source, and organic solvent are the same as described above and will not be repeated here. The second method is more preferred in this invention.

[0096] In this invention, the molar ratio between the metal in the metal source and the Ag in the silver source is preferably (20-50):1, more preferably (30-40):1, and most preferably (33-36):1. In this invention, the molar ratio between the metal in the metal source and the S / Se in the S / Se source is preferably 1:(30-90), specifically 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, or 1:90. In this invention, the amount of organic solvent is preferably such that the concentration of metal ions (i.e., metal ions in the metal source) in the mixed reaction solution (i.e., the mixture of silver source, metal source, S / Se source, and organic solvent) is 0.01-0.2 mol / L, more preferably 0.03-0.1 mol / L, and most preferably 0.03-0.05 mol / L.

[0097] In this invention, a silver source, a metal source, an S / Se source, and an organic solvent are mixed and then subjected to a heating reaction. The preferred heating rate is 5–15 °C / min, specifically 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min, 11 °C / min, 12 °C / min, 13 °C / min, 14 °C / min, or 15 °C / min. The target reaction temperature is 185–280 °C, specifically 185 °C, 190 °C, 195 °C, 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, 225 °C, 230 °C, 235 °C, 240 °C, 245 °C, 250 °C, 255 °C, 260 °C, 265 °C, 270 °C, 275 °C, or 280 °C. The reaction time (i.e., the holding time after heating to the target temperature) is preferably 30–90 min, specifically 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, and 90 min. Following the above reaction, Al-M nanowires are generated in the system.

[0098] In this invention, after the above reaction, the following post-processing is preferably performed: cooling, solid-liquid separation, and washing. The cooling method is not particularly limited and can be any cooling method well known to those skilled in the art; natural cooling is preferred in this invention. The solid-liquid separation method is preferably centrifugal separation. The washing agent is preferably at least one of n-hexane, ethanol, and propanol, more preferably n-hexane and ethanol. The washing can be performed multiple times, for example, 2 to 3 times. After the above post-processing, Al-M nanowires are obtained.

[0099] According to the preparation method of this invention, the diameter of Al-M nanowires can be precisely controlled by adjusting the reaction conditions in step A). ​​Taking the preparation of Ag2S-Co9S8 nanowires as an example, during the reaction process, as the temperature increases, Ag2S solid superionic conductor catalyst is formed first, followed by Co... 2+ and Co 3+ Cations and S 2- The anionic precursor dissociates at the solution-catalyst interface and then incorporates into the Ag₂S catalyst as a solid solution. Once the foreign atoms in the catalyst reach critical supersaturation and the reaction temperature reaches the phase transition temperature required for the solution-solid-solid catalytic growth of the Ag₂S superionic conductor, Co₉S₈ nanowires begin to precipitate layer by layer at the Ag₂S catalyst-Co₉S₈ nanowire interface and grow along the energy-preferred crystal orientation. Furthermore, Ag₂S solid superionic conductor catalysts grown at different temperatures can catalyze the growth of Ag₂S-Co₉S₈ nanowires of different diameters.

[0100] [Regarding step A2]:

[0101] In this invention, the alkylphosphine is preferably tri-n-octylphosphine and / or tributylphosphine.

[0102] In this invention, the solvent is preferably an organic solvent, more preferably at least one selected from methanol, ethanol, and isopropanol. In this invention, the volume ratio of the alkyl phosphorus to the solvent is preferably 1:(4-6), specifically 1:4, 1:5, or 1:6. This invention does not impose any particular restrictions on the method of mixing the alkyl phosphorus and the solvent; conventional mixing methods in the art are sufficient to ensure uniform mixing.

[0103] [Regarding step A3]:

[0104] In this invention, the solvent is preferably an organic solvent, more preferably at least one selected from toluene, n-hexane, and chloroform. In this invention, the preferred ratio of Al-M nanowires to solvent is 1 mg:(0.5–4) mL. This invention does not impose any particular restrictions on the method of mixing the Al-M nanowires and solvent; conventional mixing methods in the art are sufficient to ensure uniform mixing.

[0105] [Regarding step A4]:

[0106] In this invention, the preferred temperature for mixing the alkylphosphine solution with the Al-M nanowire dispersion is room temperature, specifically 15–40°C, or 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C. The preferred reaction time is 3–6 hours, specifically 3 hours, 4 hours, 5 hours, or 6 hours. The reaction is preferably carried out under stirring conditions. The stirring is preferably magnetic stirring. The stirring rate is preferably 500–1500 rpm. During the above reaction process, based on the hard and soft acid-base theory, the soft base Ag… + It is easier to combine with soft acid alkyl phosphine to form covalent complexes, thereby removing the Ag-containing A1 endpoints in the A1-M nanowires and forming colloidal M nanowires.

[0107] In this invention, after the above reaction, the following post-processing is preferably performed: solid-liquid separation and washing. The solid-liquid separation is preferably performed by centrifugation. The washing agent is preferably at least one of n-hexane, ethanol, and propanol, more preferably n-hexane and ethanol. The washing can be performed multiple times, for example, 2 to 3 times. After the above post-processing, pure colloidal M nanowires are obtained.

[0108] In this invention, the obtained pure colloidal M nanowires are preferably Co9S8 nanowires, ZnS nanowires, or ZnSe nanowires. The pure colloidal M nanowires obtained by the above preparation method of this invention have a diameter of less than 15 nm, thus truly realizing the preparation of pure colloidal M nanowire materials.

[0109] Regarding step B) :

[0110] B) The silver source solution was mixed with the dispersion of the pure colloidal M nanowires, and an ion exchange reaction was carried out to obtain M@A2 core-shell nanowires.

[0111] In this invention, the silver source solution is a solution obtained by dissolving a silver source in a solvent. Preferably, the silver source is at least one selected from silver diethyldithiocarbamate, silver acetate, and silver nitrate. The solvent is preferably at least one selected from methanol, ethanol, and isopropanol. The concentration of the silver source solution is preferably 0.02–0.1 mol / L, specifically 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, and 0.1 mol / L.

[0112] In this invention, the dispersion of pure colloidal M nanowires is a dispersion obtained by dispersing the pure colloidal M nanowires in a solvent. The solvent is preferably at least one selected from toluene, n-hexane, and chloroform. The preferred ratio of the pure colloidal M nanowires to the solvent is 1 mg:(0.5–2) mL, specifically 1 mg:0.5 mL, 1 mg:1.0 mL, 1 mg:1.5 mL, or 1 mg:2.0 mL.

[0113] In this invention, the molar ratio of silver ions in the silver source solution to metal cations in the dispersion of pure colloidal M nanowires is preferably 1:(0.1-3), specifically 1:0.1, 1:0.5, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0, and more preferably 1:(0.1-1). The volume ratio of the solvent in the silver source solution to the solvent in the dispersion of pure colloidal M nanowires is preferably 1:(0.25-3), specifically 1:0.25, 1:0.5, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0, and more preferably 1:(1-2).

[0114] In this invention, the silver source solution is mixed with the dispersion of the pure colloidal M nanowires using conventional mixing methods. However, for the preparation of ZnSe@Ag2Se core-shell nanowires, the preferred mixing method is to add the silver source solution dropwise to the dispersion of the pure colloidal M nanowires while stirring. The dropwise addition is preferably by injection. The injection dropwise addition rate is preferably 15–25 μL / s, specifically 15 μL / s, 20 μL / s, or 25 μL / s.

[0115] In this invention, stirring is preferably performed during the mixing of the silver source solution and the dispersion of the pure colloidal M nanowires and the ion exchange reaction. The stirring rate is preferably 500–1500 rpm. The temperature of the ion exchange reaction is preferably 10–40°C, specifically 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C, more preferably 20–30°C. The reaction time is preferably 5–60 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min, more preferably 20–30 min. Through the above ion exchange reaction, Ag ions in the silver source exchange with metal ions on the surface of the colloidal M nanowires, forming an Ag₂S / Ag₂Se shell on the surface of the colloidal M nanowires, thereby obtaining M@A₂ core-shell heterojunction nanowires.

[0116] In this invention, after the above-mentioned ion exchange reaction, the following post-processing is preferably performed: solid-liquid separation and washing. The solid-liquid separation is preferably performed by centrifugation. The washing agent is preferably at least one selected from n-hexane, toluene, ethanol, and acetone. The washing can be performed multiple times, for example, 2 to 3 times. After the above post-processing, M@A2 core-shell heterojunction nanowires are obtained.

[0117] In this invention, the obtained M@A2 core-shell heterojunction nanowires contain M as the core nanowire and A2 as the shell coating the surface of the core nanowire; A2 is an inorganic compound of Ag, preferably Ag2S or Ag2Se. In this invention, the M@A2 core-shell heterojunction nanowires are preferably Co9S8@Ag2S, ZnS@Ag2S, or ZnSe@Ag2Se.

[0118] Regarding step C) :

[0119] C) The M@A2 core-shell nanowires are dispersed in a solvent and then heat-treated to obtain an axially periodic core-shell nanoheterojunction material.

[0120] In this invention, the solvent is preferably an organic solvent, more preferably at least one selected from toluene, n-hexane, and chloroform, and most preferably toluene. In this invention, the preferred ratio of M@A2 core-shell nanowires to solvent is 1 mg:(0.5–2) mL. After dispersion, an M@A2 core-shell nanowire dispersion is obtained.

[0121] In this invention, after the above dispersion, the resulting dispersion is subjected to heat treatment. The preferred heat treatment temperature is 40–120°C, specifically 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C, more preferably 40–80°C. The preferred heat treatment time is 3–24 hours, more preferably 8–12 hours. Through the above heat treatment, the uniform core-shell heterojunction nanowires obtained in step B) undergo structural evolution, utilizing the Rayleigh fluid instability in inorganic solids to cause deformation, resulting in axially periodic core-shell heterojunctions. The structural evolution process from the pure colloidal M nanowires obtained in step A) → the M@A2 core-shell nanowires obtained in step B) → the axially periodic core-shell nanoheterojunctions obtained in step C) is described below. Figure 2In this invention, the obtained axially periodic core-shell nanoheterojunction structure is -[M@A2]-M-, preferably including -[Co9S8@Ag2S]-Co9S8-, -[ZnS@Ag2S]-ZnS-, -[ZnSe@Ag2Se]-ZnSe-, etc.; taking -[Co9S8@Ag2S]-Co9S8- as an example, it represents an ordered structure composed of Co9S8 nanowire units and Co9S8@Ag2S core-shell heterojunction nanowire units arranged in a periodic alternation along the axial direction, and other products are deduced by analogy.

[0122] The preparation method provided by this invention first uses a catalytic growth method to obtain A1-M nanowires with endpoints, and then removes the endpoints A1 of the A1-M nanowires with alkylphosphine to obtain pure colloidal M nanowires. Next, a silver source solution is mixed with a dispersion of the pure colloidal M nanowires for an ion exchange reaction to obtain M@A2 uniform core-shell heterojunction nanowires. Finally, the M@A2 core-shell nanowires are dispersed in a solvent and subjected to heat treatment. The Rayleigh fluid instability in inorganic solids causes deformation, leading to structural evolution of the uniform core-shell heterojunction nanowires to obtain axially periodic core-shell heterojunctions. Compared with existing technologies, this invention, for the first time, utilizes the principle of Rayleigh fluid instability in inorganic solids to precisely synthesize axially periodic nanoheterostructures with adjustable size and periodicity, opening a new avenue for the design and synthesis of axially periodic nanoheterostructures.

[0123] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0124] Example 1

[0125] 1. Sample preparation:

[0126] A) Preparation of Co9S8 nanowires:

[0127] A1) 5 mg of silver diethyldithiocarbamate, 200 mg of cobalt nitrate, 10 mL of dodecanethiol, and 10 mL of oleic acid were mixed in a 25 mL three-necked flask. The mixture was heated to 210 °C at a rate of 10 °C / min and held at that temperature for 60 min. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, centrifuged, and washed three times with n-hexane and ethanol to obtain Ag₂S-Co₉S₈ nanowires with endpoints.

[0128] A2) Mix 2 mL of tributylphosphine with 10 mL of methanol to obtain a tributylphosphine solution.

[0129] A3) Take 40 mg of Ag2S-Co9S8 nanowires obtained in step A1) and disperse them in 20 mL of chloroform to obtain Ag2S-Co9S8 nanowire dispersion.

[0130] A4) Add the tributylphosphine solution obtained in step A2) to the Ag2S-Co9S8 nanowire dispersion obtained in step A3), and stir magnetically (1000 rpm) for 4 h at room temperature. After the reaction is complete, centrifuge the product and wash it three times with n-hexane and ethanol to obtain pure Co9S8 nanowires.

[0131] B) Preparation of Co9S8@Ag2S core-shell heterostructure nanowires:

[0132] B1) Mix silver nitrate with methanol to obtain a silver nitrate solution (concentration 0.024 mol / L).

[0133] B2) Disperse the pure Co9S8 nanowires obtained in step A) into toluene to obtain a Co9S8 nanowire dispersion (the ratio of Co9S8 nanowires to toluene is 1 mg: 1 mL).

[0134] B3) A silver nitrate solution and a Co9S8 nanowire dispersion were mixed (the molar ratio of Ag ions in the silver source solution to Co ions in the Co9S8 nanowires was preferably 1:1). After thorough mixing, the mixture was reacted at 25°C for 30 min. Then, centrifugation and washing were performed to obtain Co9S8@Ag2S core-shell heterojunction nanowires.

[0135] C) Preparation of [Co9S8@Ag2S]-Co9S8-axially periodic core-shell nanoheterostructures:

[0136] Take 20 mg of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B), disperse them in 20 mL of toluene to obtain a Co9S8@Ag2S core-shell heterojunction nanowire dispersion; then heat it to 80 °C for 12 h to obtain -[Co9S8@Ag2S]-Co9S8- axial periodic core-shell nanoheterojunctions.

[0137] 2. Sample Characterization

[0138] The Co9S8 nanowires obtained in step A) were analyzed using transmission electron microscopy, and their transmission electron micrographs were obtained, as shown below. Figure 3 As shown, the obtained Co9S8 nanowires have good morphology and uniform size, and good dispersibility.

[0139] The Co9S8@Ag2S core-shell heterostructure nanowires obtained in step B) were analyzed using transmission electron microscopy, and their transmission electron microscopy images are shown below. Figure 4As shown, the obtained Co9S8@Ag2S core-shell heterojunction nanowires exhibit a distinct core-shell structure and a uniform size distribution.

[0140] EDS analysis was performed on the Co9S8@Ag2S core-shell heterostructure nanowires obtained in step B), and the results are as follows: Figure 5-7 As shown, where, Figure 5 The image shows the EDS elemental surface analysis of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1. Figure 6 This is an EDS line scan of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1. Figure 7 The image shown is the EDS spectrum of the Co9S8@Ag2S core-shell heterojunction nanowires obtained in step B) of Example 1. Figure 5 , Figure 6 and Figure 7 The core-shell structure of the obtained product can be seen.

[0141] The axially periodic core-shell nanoheterostructures obtained in step C) were analyzed using transmission electron microscopy, such as... Figure 8-9 As shown. Among them, Figure 8 This is a transmission electron microscope image of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1. Figure 9 The image shown is a dark-field transmission electron microscope image of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1. It can be seen that the obtained product has a uniform morphology and exhibits an axially periodic distribution.

[0142] EDS analysis was performed on the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C), and the results are as follows: Figure 10-12 As shown, where, Figure 10 The image shows the EDS elemental surface analysis of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1. Figure 11 The image shown is an EDS line scan of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1. Figure 12 The image shows the EDS spectrum of the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C) of Example 1. Figure 10 , Figure 11 and Figure 12 The axial periodic distribution of the obtained products can be observed.

[0143] X-ray diffraction tests were performed on the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C), and the results are as follows: Figure 13 As shown, the obtained product is highly consistent with the Ag2S phase (JCPDS: 89-3840).

[0144] High-resolution transmission electron microscopy analysis was performed on the -[Co9S8@Ag2S]-Co9S8- axially periodic core-shell nanoheterostructure obtained in step C), and the results are as follows: Figure 14 As shown, the Co9S8 core and the Ag2S shell have a high degree of lattice matching.

[0145] Example 2

[0146] 1. Sample preparation

[0147] A) Preparation of ZnS nanowires:

[0148] A1) 5 mg of silver diethyldithiocarbamate, 235 mg of zinc diethyldithiocarbamate, and 10 mL of dodecanethiol were mixed in a 25 mL three-necked flask. The mixture was heated to 210 °C at a rate of 10 °C / min, followed by the addition of 10 mL of oleic acid. After the temperature returned to 210 °C, the mixture was kept at this temperature for 60 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, centrifuged, and washed three times with n-hexane and ethanol to obtain Ag₂S-ZnS nanowires with endpoints.

[0149] A2) Mix 2 mL of tributylphosphine with 10 mL of methanol to obtain a tributylphosphine solution.

[0150] A3) Take 40 mg of Ag2S-ZnS nanowires obtained in step A1) and disperse them in 20 mL of chloroform to obtain Ag2S-ZnS nanowire dispersion.

[0151] A4) Add the tributylphosphine solution obtained in step A2) to the Ag2S-ZnS nanowire dispersion obtained in step A3), and stir magnetically (1000 rpm) for 4 h at room temperature. After the reaction is complete, centrifuge the product and wash it three times with n-hexane and ethanol to obtain pure ZnS nanowires.

[0152] B) Preparation of ZnS@Ag2S core-shell heterostructure nanowires:

[0153] B1) Mix silver nitrate with methanol to obtain a silver nitrate solution (concentration 0.02 mol / L).

[0154] B2) Disperse the pure ZnS nanowires obtained in step A) into toluene to obtain a ZnS nanowire dispersion (the ratio of ZnS nanowires to toluene is 1 mg: 0.5 mL).

[0155] B3) A silver nitrate solution and a ZnS nanowire dispersion were mixed (the molar ratio of Ag ions in the silver source solution to Zn ions in the ZnS nanowires was preferably 1:1). After thorough mixing, the mixture was reacted at 25°C for 30 min. Then, centrifugation and washing were performed to obtain ZnS@Ag2S core-shell heterojunction nanowires.

[0156] C) Preparation of [ZnS@Ag2S]-ZnS-axially periodic core-shell nanoheterostructures:

[0157] Take 10 mg of the ZnS@Ag2S core-shell heterojunction nanowires obtained in step B), disperse them in 20 mL of toluene to obtain a ZnS@Ag2S core-shell heterojunction nanowire dispersion; then heat it to 60 °C for 6 h to obtain -[ZnS@Ag2S]-ZnS-axial periodic core-shell nanoheterojunctions.

[0158] 2. Sample Characterization

[0159] The ZnS nanowires obtained in step A) were analyzed using transmission electron microscopy, and their transmission electron micrographs were obtained, as shown in the figure. Figure 15 As shown in the figure, the obtained ZnS nanowires have good morphology and uniform size, and good dispersion.

[0160] The ZnS@Ag2S core-shell heterostructure nanowires obtained in step B) were analyzed using transmission electron microscopy, and their transmission electron microscopy images are shown below. Figure 16 As shown, the obtained ZnS@Ag2S core-shell heterojunction nanowires exhibit a distinct core-shell structure and a uniform size distribution.

[0161] EDS elemental surface analysis was performed on the ZnS@Ag2S core-shell heterostructure nanowires obtained in step B), and the results are as follows: Figure 17 As shown, the obtained ZnS@Ag2S core-shell heterojunction nanowires have a distinct and uniform core-shell structure.

[0162] The axially periodic core-shell nanoheterostructures obtained in step C) were analyzed using transmission electron microscopy, such as... Figure 18 As shown, the resulting products exhibit an axially periodic distribution.

[0163] EDS elemental surface analysis was performed on the -[ZnS@Ag2S]-ZnS-axially periodic core-shell nanoheterostructure obtained in step C), and the results are as follows: Figure 19 As shown, it can be seen that the obtained products exhibit an axially periodic distribution.

[0164] Example 3

[0165] 1. Sample preparation

[0166] A) Preparation of ZnSe nanowires:

[0167] A1) 78 mg of selenium powder was dispersed in 10 mL of oleylamine, and the temperature was increased to 250 °C at a rate of 10 °C / min. After reacting for 30 min, a selenylamine solution was obtained. 34 mg of silver nitrate and 2 mL of selenylamine were dispersed in 8 mL of oleylamine, and the temperature was increased to 120 °C at a rate of 10 °C / min. After reacting for 60 min, an Ag₂Se catalyst was obtained. 1.5 mL of the catalyst was centrifuged and dispersed in 1 mL of oleylamine to obtain an Ag₂Se dispersion. The Ag₂Se dispersion, 72 mg of selenium dioxide, and 120 mg of zinc acetate were dispersed in 9 mL of oleylamine solution, and the temperature was increased to 210 °C at a rate of 10 °C / min. After reacting for 30 min, Ag₂Se-ZnSe nanowires were obtained.

[0168] A2) Mix 2 mL of tributylphosphine with 10 mL of methanol to obtain a tributylphosphine solution.

[0169] A3) Take 40 mg of Ag2Se-ZnSe nanowires obtained in step A1) and disperse them in 20 mL of chloroform to obtain Ag2Se-ZnSe nanowire dispersion.

[0170] A4) Add the tributylphosphine solution obtained in step A2) to the Ag2Se-ZnSe nanowire dispersion obtained in step A3), and stir magnetically (1000 rpm) for 4 h at room temperature. After the reaction is complete, centrifuge the product and wash it three times with n-hexane and ethanol to obtain pure ZnSe nanowires.

[0171] B) Preparation of ZnSe@Ag2Se core-shell heterostructure nanowires:

[0172] B1) Mix silver nitrate with methanol to obtain a silver nitrate solution (concentration 0.04 mol / L).

[0173] B2) Disperse the pure ZnSe nanowires obtained in step A) into chloroform and oleylamine to obtain a ZnSe nanowire dispersion (the volume ratio of ZnSe nanowires to solvent is 1 mg: 1 mL; the volume ratio of chloroform to oleylamine in the solvent is 1: 0.25).

[0174] B3) Silver nitrate solution was added dropwise to the ZnSe nanowire dispersion using injection molding (the molar ratio of Ag ions in the silver source solution to Zn ions in the ZnSe nanowires was preferably 1:1). The injection rate was 20 μL / s, and the reaction was carried out at 25°C for 30 min under magnetic stirring at 1000 rpm. Then, centrifugation and washing were performed to obtain ZnSe@Ag2Se core-shell heterojunction nanowires.

[0175] C) Preparation of [ZnSe@Ag2Se]-ZnSe-axially periodic core-shell nanoheterostructures:

[0176] Take 10 mg of the ZnSe@Ag2Se core-shell heterojunction nanowires obtained in step B), disperse them in 20 mL of toluene to obtain a ZnSe@Ag2Se core-shell heterojunction nanowire dispersion; then heat it to 60 °C for 3 h to obtain -[ZnSe@Ag2Se]-ZnSe-axial periodic core-shell nanoheterojunctions.

[0177] 2. Sample Characterization

[0178] The ZnSe nanowires obtained in step A) were analyzed using transmission electron microscopy, and their transmission electron micrographs were obtained, as shown below. Figure 20 As shown, the obtained ZnSe nanowires have good morphology and uniform size, and good dispersibility.

[0179] The ZnSe@Ag2Se core-shell heterostructure nanowires obtained in step B) were analyzed using transmission electron microscopy, and their transmission electron microscopy images are shown below. Figure 21 As shown, the obtained ZnSe@Ag2Se core-shell heterojunction nanowires exhibit a distinct core-shell structure and a uniform size distribution.

[0180] EDS elemental surface analysis was performed on the ZnSe@Ag2Se core-shell heterostructure nanowires obtained in step B), and the results are as follows: Figure 22 As shown, the obtained ZnS@Ag2S core-shell heterojunction nanowires have a distinct and uniform core-shell structure.

[0181] The axially periodic core-shell nanoheterostructures obtained in step C) were analyzed using transmission electron microscopy, such as... Figure 23 As shown, the resulting products exhibit an axially periodic distribution.

[0182] EDS elemental surface analysis was performed on the -[ZnSe@Ag2Se]-ZnSe-axially periodic core-shell nanoheterostructure obtained in step C), and the results are as follows: Figure 24 As shown, the resulting products exhibit an axially periodic distribution.

[0183] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing an axially periodic core-shell nanoheterostructure material, characterized in that, The method comprises the following steps: A) preparing A1-M nanowires by using a catalytic growth method, and then removing end-point A1 in the A1-M nanowires by using alkyl phosphine to obtain pure colloid M nanowires; In the A1-M nanowires, A1 is an inorganic compound of Ag; and M is Co9S8 or ZnSe; B) mixing a silver source solution with a dispersion liquid of the pure colloid M nanowires to perform an ion exchange reaction, so as to obtain M@A2 core-shell nanowires; In the method, the silver source solution is a solution obtained by dissolving a silver source in a solvent; the dispersion liquid of the pure colloid M nanowires is a dispersion liquid obtained by dispersing the pure colloid M nanowires in a solvent; and in the M@A2 core-shell nanowires, M is a core nanowire, A2 is a shell layer covering the surface of the core nanowire, and A2 is an inorganic compound of Ag. C) dispersing the M@A2 core-shell nanowires into a solvent, and then performing heat treatment, so as to obtain an axial periodic core-shell nanoheterojunction material. In step B), the ion exchange reaction is performed at a temperature of 10-40 ℃ for 5-60 min. In step C), the heat treatment is performed at a temperature of 40-120 ℃ for 3-24 h. In step B), the silver source is at least one of silver diethyldithiocarbamate, silver acetate and silver nitrate.

2. The production method according to claim 1, characterized by, In step B), the molar ratio of silver ions in the silver source solution to metal cations in the dispersion liquid of the pure colloid M nanowires is 1:(0.1-3).

3. The method of claim 1, wherein, In step C), the solvent is at least one of toluene, n-hexane and chloroform; and the use amount ratio of the M@A2 core-shell nanowires to the solvent is 1 mg:(0.5-2) mL.

4. The method of claim 1, wherein, Step A) specifically comprises:

5. The preparation method according to claim 1, characterized in that, A1) mixing a silver source, a metal source, an S / Se source and an organic solvent to perform a heating reaction, so as to obtain A1-M nanowires; 6. The method of claim 1, wherein, A2) mixing alkyl phosphine with a solvent to obtain an alkyl phosphine solution; A3) mixing the A1-M nanowires with a solvent to obtain an A1-M nanowire dispersion liquid; A4) mixing the alkyl phosphine solution with the A1-M nanowire dispersion liquid to perform a reaction, so as to obtain pure colloid M nanowires; 7. The preparation method according to claim 1, characterized in that, In the method, steps A1) and A2) are not limited in sequence, and steps A2) and A3) are not limited in sequence. In step A1), the reaction is performed at a temperature of 185-280 ℃ for 30-90 min. In step A2), the alkyl phosphine is tri-n-octylphosphine and / or tributylphosphine. In step A4), the reaction is performed at a temperature of 15-40 ℃ for 3-6 h. In the A1-M nanowires, the diameter of the end-point A1 is 4-20 nm; The diameter of the A1-M nanowires is 4-20 nm; 8. The preparation method according to claim 7, characterized in that, The length of the A1-M nanowires is 20-3000 nm. The M@A2 core-shell nanowires obtained in step B) comprise Co9S8@Ag2S core-shell nanowires or ZnSe@Ag2Se core-shell nanowires. The axial periodic core-shell nanoheterojunction material obtained in step C) comprises a-[Co9S8@Ag2S]-Co9S8 axial periodic core-shell nanoheterojunction or a-[ZnSe@Ag2Se]-ZnSe axial periodic core-shell nanoheterojunction.

9. The method of claim 1, wherein, ​ ​ ​ 10. The method of claim 1, wherein, ​ ​

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