A controllable preparation method of nanometer superlattice material

Abstract

This invention relates to a controllable preparation method for a nanocrystalline superlattice material. First, polyethylene glycol-grafted gold nanospheres with a flexibility λ of 0.57 are dispersed in deionized water to prepare a PEG@NPs solution. Then, an aqueous solution of an inorganic salt (soluble carbonate or soluble sulfate) is added to the PEG@NPs solution, and after mixing thoroughly, the mixture is allowed to stand to obtain the nanocrystalline superlattice material. When the concentration of the inorganic salt aqueous solution is 0.60–0.70 M, the nanocrystalline superlattice material is a three-dimensional ordered nanocrystalline superlattice material; when the concentration of the inorganic salt aqueous solution is 0.50–0.55 M, the nanocrystalline superlattice material is a two-dimensional ordered nanocrystalline superlattice material. The flexibility λ is defined as: λ = R0 / R c Where R0 is the mean square end-to-end distance of the polyethylene glycol (PEG) molecular chain, R0 = bN12, b is the length of the PEG Kuhn segment, and N is the number of PEG Kuhn segments. c The radius is denoted as . This invention enables precise control over the dimensions of the superlattice by simply changing the salt solution concentration.

Description

Technical Field

[0001] This invention belongs to the field of superlattice materials technology and relates to a controllable preparation method for nano-superlattice materials. Background Technology

[0002] Analogous to atomic or molecular crystals, superlattices are highly ordered novel materials formed by the self-assembly of nanoparticles through interactions with themselves or surface ligands. Unlike individual nanoparticles, nanocrystalline superlattices exhibit unique collective synergistic effects due to their ordered periodic structure, showing significant application prospects in numerous fields such as electronic devices, photoelectric conversion, high-efficiency catalysis, and medical biology. Therefore, manipulating the precise assembly of nanoparticles at the microscale to construct superlattice materials with specific structures and functions can greatly enrich the diversity and functionality of macroscopic materials, and is key to further promoting the development of nanomaterial device technology.

[0003] Just as atoms can be manipulated to form molecules or molecules can be assembled into more complex supramolecular structures through synthesis, the precise assembly of nanoparticles into highly ordered nanocrystalline superlattices is a research hotspot and challenge in the field of nanoscience. Among these, the "bottom-up" self-assembly method is considered one of the most promising strategies for constructing nanocrystalline superlattices. This method refers to the process by which nanoparticles spontaneously form ordered structures under non-covalent interactions. By controlling the weak chemical interactions of nanoparticles during the assembly process, the controllable assembly of superlattices with different structures can be achieved. For example, CN112745849A discloses a method for preparing a binary nanocrystalline superlattice material self-assembled from lanthanide-doped upconversion luminescent nanocrystals and gold nanoparticles. CN110745792A reports a method for preparing a monolayer alternating stacked g-C3N4-based two-dimensional superlattice.

[0004] Research has found that the construction of nanocrystalline superlattices typically takes only a few kJ / k ... B Within the energy range of T, the equilibrium of various forces between nanoparticles is the result of mutual balance. However, due to the narrow experimental window required for this force balance, nanoparticles often fail to achieve their most thermodynamically stable state, exhibiting numerous thermodynamically metastable states. This reduces the orderliness of the assembled structure, significantly limiting the construction and application of highly ordered superlattices. Currently, the main methods for preparing nanocrystalline superlattices are solvent evaporation and solution destabilization. Solvent evaporation involves the slow evaporation of the solvent to form a two-dimensional superlattice film, while solution destabilization primarily involves the introduction or enrichment of undesirable solvents to induce nanoparticle instability and aggregation, forming a three-dimensional nanocrystalline superlattice structure. However, due to the complexity of nanoparticle motion in solution and the uncontrollability of the driving forces during assembly, these two methods are currently insufficient for constructing nanocrystalline superlattice materials with controllable and tunable dimensions and morphology.

[0005] The Hofmeister effect refers to the precipitation of proteins from aqueous solutions by adding salt. Furthermore, research has found that the addition of certain anions can polarize hydrated water molecules, thereby disrupting the hydrogen bonds between water-soluble polymers and hydrated water molecules. By changing the type and concentration of the added salt, the degree of hydration of the water-soluble polymer ligands can be precisely controlled. Therefore, the Hofmeister effect provides a new approach and method for precisely controlling the interactions between water-soluble polymer-modified nanoparticles, achieving controllable and tunable dimensions and morphologies of nanocrystalline superlattices in solution systems. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems in the prior art and to provide a controllable preparation method for nanoscale superlattice materials.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A controllable preparation method for a nano-superlattice material involves first dispersing polyethylene glycol-grafted gold nanospheres (PEG@NPs) with a softness λ of 0.57 in deionized water to prepare a PEG@NPs solution, then adding an inorganic salt aqueous solution to the PEG@NPs solution, mixing evenly, and allowing it to stand under conditions without human intervention or external environmental interference to obtain the nano-superlattice material.

[0009] When the concentration of the inorganic salt aqueous solution is 0.60–0.70 M, the nano-superlattice material is a three-dimensional ordered nanocrystalline superlattice material;

[0010] When the concentration of the inorganic salt aqueous solution is 0.50–0.55 M, the nano-superlattice material is a two-dimensional ordered nanocrystalline superlattice material;

[0011] The inorganic salt is a soluble carbonate or a soluble sulfate;

[0012] The softness λ is defined as:

[0013] λ=R0 / R c ;

[0014] Where R0 is the mean square end-to-end distance of the polyethylene glycol molecular chain, R0 = bN 12 , b is the length of the polyethylene glycol Kuhn segment, with a value of N is the number of polyethylene glycol Kuhn segments, R c This refers to the radius of the gold nanospheres (after grafting, the overall size will change, including the size of the gold nanospheres themselves and the thickness of the grafted polyethylene glycol; here we are referring to the radius of the gold nanospheres themselves, excluding the thickness of the grafted polyethylene glycol).

[0015] As a preferred technical solution:

[0016] The controllable preparation method of the nano-superlattice material described above requires a settling time of 3 days.

[0017] In the controllable preparation method of the nano-superlattice material described above, the concentration of the PEG@NPs solution is 150–200 nM.

[0018] In the controllable preparation method of the nano-superlattice material described above, the volume ratio of PEG@NPs solution to inorganic salt aqueous solution is 1:10.

[0019] The controllable preparation method of the nano-superlattice material described above uses potassium carbonate, sodium carbonate, or ammonium carbonate as the soluble carbonate and potassium sulfate, sodium sulfate, ammonium sulfate, or magnesium sulfate as the soluble sulfate.

[0020] The controllable preparation method of the nano-superlattice material described above, the preparation method of polyethylene glycol-grafted gold nanospheres is as follows: a thiol-modified polyethylene glycol solution is added to a citrate-modified gold nanosphere solution, mixed evenly, and reacted at room temperature (25°C) for 12-24 hours to obtain polyethylene glycol-grafted gold nanospheres through ligand exchange.

[0021] In the controllable preparation method of the nano-superlattice material described above, the concentration of the thiol-modified polyethylene glycol solution is 1.0–2.0 mM, and the concentration of the citrate-modified gold nanosphere solution is 0.5–5.0 nM.

[0022] In the controllable preparation method of the nano-superlattice material described above, the molar ratio of thiol-modified polyethylene glycol to citrate-modified gold nanospheres is 3000–10000:1.

[0023] The controllable preparation method of the nano-superlattice material described above uses thiol-modified polyethylene glycol with a number-average molecular weight of 1000 to 10000.

[0024] The principle of this invention is as follows:

[0025] The self-assembly behavior of polymer-grafted nanoparticles exhibits a significant softness-dependent characteristic (ACS Nano, 2020. DOI: 10.1021 / acsnano.0c00668. https: / / pubs.acs.org / doi / 10.1021 / acsnano.0c00668). Softness is a simple yet powerful tool for designing nanoscale superlattices with precisely controlled interparticle distances and varying packing symmetries. When polyethylene glycol-grafted gold nanospheres with specific softness are dispersed in low-concentration solutions of soluble carbonates or sulfates, based on the Hofmeister series effect, a small amount of carbonate or sulfate ions in the solution can disrupt the hydrogen bonds between water-soluble polyethylene glycol and hydrated water molecules. This causes some water molecules to be expelled from the polyethylene glycol molecular chains, resulting in a gradual transformation of polyethylene glycol from hydrophilic to hydrophobic. At lower salt solution concentrations, the degree of hydrophobic transformation of polyethylene glycol (PEG) is weaker. Under the relatively weak hydrophobic interactions between PEG molecular chains, nanoparticles tend to laterally form two-dimensional monolayer superlattice materials. As the salt solution concentration increases, the presence of numerous carbonate ions disrupts more hydrogen bonds between water-soluble PEG and water molecules, thus increasing the degree of hydrophobic transformation of PEG. Ultimately, under the stronger hydrophobic interactions between PEG molecular chains, nanoparticles tend to laterally and longitudinally form three-dimensional superlattice materials. When the flexibility is low (i.e., the polymer ligand length is shorter than the inorganic core radius), van der Waals interactions between inorganic cores play a major role in nanoparticle assembly. Adjusting the salt solution concentration has little effect on van der Waals interactions; ultimately, strong van der Waals forces between inorganic cores drive the rapid assembly of nanoparticles into disordered aggregates. When the flexibility is high (i.e., the polymer ligand length is longer than the inorganic core radius), interactions between polymer ligands play a major role in nanoparticle assembly. The hydrophobic interactions between polymer ligands can be modulated by changing the salt solution concentration. However, enhanced hydrophobic interactions lead to closer proximity of nanoparticles, increasing the volume repulsion between ligand molecular chains. This causes the nanoparticles to tend to assemble into a monolayer superlattice film under stronger volume repulsion. Through repeated experiments, this invention has shown that only when the flexibility is within the specific value specified in this invention do the inorganic internuclear van der Waals forces and polymer ligand interactions work together. By adjusting the salt solution concentration, the values ​​of these two forces can be controlled, thereby achieving the control of the superlattice dimension.

[0026] Beneficial effects:

[0027] (1) This invention provides a controllable preparation method for nanocrystalline superlattices. By simply changing the salt solution concentration, the dimensions of the superlattice can be precisely controlled, and two-dimensional and three-dimensional highly ordered nanocrystalline superlattices can be prepared. The preparation method is simple and easy to control, and is convenient for industrial production.

[0028] (2) The softness parameter proposed in this invention can guide the design of nanocrystalline superlattice materials with adjustable particle spacing and different dimensions, which is crucial for applications in magnetism, plasma electronics and electronics.

[0029] (3) This invention provides a simple and reliable softness parameter for predicting interparticle distance and self-assembly behavior, which is crucial for the rational design of functional nanostructure materials. Attached Figure Description

[0030] Figure 1 The flowcharts are for the preparation of Examples 1 and 3.

[0031] Figure 2 High-resolution scanning electron microscope (SEM) images of the three-dimensional nano-superlattice material prepared in Example 1: (a) High-resolution scanning electron microscope image of the three-dimensional superlattice; (b) SEM magnification of the single crystal surface; (c) SEM magnification of the single crystal side surface.

[0032] Figure 3 SAXS diagram of the three-dimensional nano-superlattice material prepared in Example 1;

[0033] Figure 4 Here is a high-resolution scanning electron microscope image of the two-dimensional nano-superlattice material prepared in Example 2;

[0034] Figure 5 The images are transmission electron microscope (TEM) images of the two-dimensional nano-superlattice material prepared in Example 2: (a) a low-magnification TEM image of the two-dimensional nano-superlattice material; (b) a low-magnification TEM image of the two-dimensional nano-superlattice material.

[0035] Figure 6 High-resolution scanning electron microscope image of the monolayer superlattice thin film prepared in Comparative Example 1;

[0036] Figure 7 High-resolution scanning electron microscope image of the disordered aggregates prepared for Comparative Example 2. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] In this invention, the softness λ is defined as: λ = R0 / R c Where R0 is the mean square end-to-end distance of the polyethylene glycol molecular chain, R0 = bN 12, b is the length of the polyethylene glycol Kuhn segment, with a value of N is the number of polyethylene glycol Kuhn segments, R c Let be the radius of the gold nanosphere.

[0039] Example 1

[0040] A method for preparing a nanoscale superlattice material, such as Figure 1 As shown, the specific steps are as follows:

[0041] (1) Dissolve the thiol-modified polyethylene glycol (number average molecular weight of 1000) solid powder completely in deionized water to prepare a thiol-modified polyethylene glycol solution with a concentration of 1.0 mM.

[0042] (2) According to the molar ratio of thiol-modified polyethylene glycol to citrate-modified gold nanospheres of 5000:1, the thiol-modified polyethylene glycol solution obtained in step (1) was added to a citrate-modified gold nanosphere solution (average diameter of 19.3 nm) with a concentration of 1.2 nM. After mixing evenly, the mixture was reacted at 25 °C for 24 h. Through ligand exchange, polyethylene glycol-grafted gold nanospheres (PEG@NPs) with a softness λ of 0.57 were obtained.

[0043] (3) Disperse the polyethylene glycol-grafted gold nanospheres with a softness λ of 0.57 obtained in step (2) into deionized water to prepare a PEG@NPs solution with a concentration of 150 nM.

[0044] (4) Add a 0.65M potassium carbonate aqueous solution to the PEG@NPs solution obtained in step (3) according to the volume ratio of PEG@NPs solution to inorganic salt aqueous solution of 1:10. After mixing evenly, let stand for 3 days to obtain a three-dimensional ordered nano-superlattice material.

[0045] Without the addition of potassium carbonate solution, PEG@NPs nanoparticles are monodisperse in aqueous solution. When 0.65M potassium carbonate solution is added to the system, carbonate ions begin to break the hydrogen bonds between water-soluble polyethylene glycol and hydrated water molecules, thereby expelling some water molecules from between the polyethylene glycol molecular chains, causing polyethylene glycol to change from hydrophilic to hydrophobic.

[0046] The morphology and structure of the prepared three-dimensional ordered nano-superlattice material were analyzed using high-resolution scanning electron microscopy, such as... Figure 2 As shown in (a), the nanoparticles slowly approach each other due to the strong hydrophobic interaction between the polyethylene glycol molecular chains, achieving a balance between the attractive and repulsive forces between the nanoparticles, and ultimately assembling into a hexagonal superlattice single crystal with a size of approximately 1.5 μm; from Figure 2 (b) It can be clearly seen that the nanoparticles on the single crystal surface exhibit a highly ordered hexagonal stacking and periodic arrangement; from Figure 2 (c) It can be seen that the nanoparticles exhibit a typical ABC stacking pattern between layers, that is, the prepared single crystal is a body-centered cubic superlattice.

[0047] The internal microstructure of three-dimensional ordered nanoscale superlattice materials was characterized using small-angle scattering (SAXS) technology, such as... Figure 3 As shown. The SAXS images obtained from the characterization show four distinct characteristic scattering peaks at positions (111), (200), (220), and (311), further indicating that the assembled three-dimensional ordered superlattice is a high-quality body-centered cubic superlattice. The distance (d) between the nearest neighbor nanoparticles is given by the formula... The result shows that q0 represents the position of the first diffraction peak. Calculations show that the nearest neighbor spacing of the prepared body-centered cubic superlattice nanoparticles is 24.5 nm.

[0048] Comparative Example 1

[0049] A method for preparing a single-layer superlattice thin film is basically the same as in Example 1, except that the average diameter of the citrate-modified gold nanospheres in step (2) is 16.7 nm, resulting in a softness λ of 0.67 for the polyethylene glycol-grafted gold nanospheres. By changing the salt solution concentration, only two-dimensional ordered superlattice thin films can be obtained; the gold nanospheres cannot be assembled to form three-dimensional superlattice materials, such as... Figure 6 As shown, it is impossible to control the superlattice dimension by adjusting the salt solution concentration.

[0050] Comparing Comparative Example 1 with Example 1, it can be found that a softness λ greater than 0.57 cannot assemble into a three-dimensional superlattice material. This is because when the softness is large, that is, when the length of the polymer ligand is longer than the radius of the inorganic core, the polymer ligand plays an important role in the assembly process of nanoparticles. The longer ligand length increases the volume repulsion force between nanoparticles, making the nanoparticles tend to assemble into a single-layer superlattice film under strong repulsion.

[0051] Comparative Example 2

[0052] A method for preparing disordered aggregates is basically the same as in Example 1, except that in step (2), the average diameter of the citrate-modified gold nanospheres is 31.2 nm, resulting in a softness λ of 0.52 for the polyethylene glycol-grafted gold nanospheres. The final product is entirely assembled into disordered aggregates, unable to form two-dimensional or three-dimensional superlattice materials, such as... Figure 7 As shown.

[0053] Comparing Comparative Example 2 with Example 1, it can be found that if the softness λ is less than 0.57, it is impossible to assemble into two-dimensional or three-dimensional superlattice materials. This is because when the softness is small, that is, when the length of the polymer ligand is shorter than the radius of the inorganic core, the van der Waals forces between the inorganic cores play an important role in the assembly process of nanoparticles. Ultimately, the strong van der Waals forces between the inorganic cores drive the rapid assembly of nanoparticles into disordered aggregate materials.

[0054] Example 2

[0055] A method for preparing a nano-superlattice material is basically the same as in Example 1, except that the “potassium carbonate aqueous solution with a concentration of 0.65M” in step (4) is replaced with “potassium carbonate aqueous solution with a concentration of 0.55M”. The final result of step (4) is a two-dimensional ordered nano-superlattice material.

[0056] After dispersing PEG@NPs nanoparticles in a 0.55M potassium carbonate solution, the morphology and structure of the assembled structure were characterized by high-resolution scanning electron microscopy. Figure 4 As shown, when the concentration of the added salt solution is reduced, a large number of uniformly sized sheet-like structures are assembled in the solution, such as... Figure 4 As shown in (a); the dimensions of the lamellar structures in the scanning electron microscope were statistically analyzed, and the results are as follows. Figure 4 As shown in (b), the diameter (D) of the prepared sheet is approximately 5.2 μm.

[0057] The microstructure of the prepared sheet-like structures was characterized using transmission electron microscopy, such as... Figure 5 As shown, it can be clearly seen that the assembled sheet assembly is a single layer, and the nanoparticles exhibit a large-scale, highly ordered hexagonal stacking periodic arrangement, such as... Figure 5 As shown in (a); by measuring the distance between the two nearest nanoparticles in a high-magnification transmission electron microscope image, the nearest nanoparticle spacing was found to be 26.5 nm, as shown in (a). Figure 5 As shown in (b).

[0058] Example 3

[0059] A method for preparing a nanoscale superlattice material, such as Figure 1 As shown, the specific steps are as follows:

[0060] (1) Dissolve the thiol-modified polyethylene glycol (number average molecular weight of 2000) solid powder completely in deionized water to prepare a thiol-modified polyethylene glycol solution with a concentration of 1.5 mM.

[0061] (2) According to the molar ratio of thiol-modified polyethylene glycol to citrate-modified gold nanospheres of 3000:1, the thiol-modified polyethylene glycol solution obtained in step (1) was added to a 5.0 nM citrate-modified gold nanosphere solution (average diameter of 28.2 nm). After mixing evenly, the mixture was reacted at 25 °C for 12 h. Through ligand exchange, polyethylene glycol-grafted gold nanospheres (PEG@NPs) with a softness λ of 0.57 were obtained.

[0062] (3) Disperse the polyethylene glycol-grafted gold nanospheres with a softness λ of 0.57 obtained in step (2) into deionized water to prepare a PEG@NPs solution with a concentration of 150 nM.

[0063] (4) Add a 0.60M potassium carbonate aqueous solution to the PEG@NPs solution obtained in step (3) according to the volume ratio of PEG@NPs solution to inorganic salt aqueous solution of 1:10. After mixing evenly, let stand for 3 days to obtain a three-dimensional ordered nano-superlattice material.

[0064] Example 4

[0065] A method for preparing a nanoscale superlattice material, the specific steps of which are as follows:

[0066] (1) Dissolve the thiol-modified polyethylene glycol (number average molecular weight of 5000) solid powder completely in deionized water to prepare a 2.0 mM thiol-modified polyethylene glycol solution.

[0067] (2) According to the molar ratio of thiol-modified polyethylene glycol to citrate-modified gold nanospheres of 10000:1, the thiol-modified polyethylene glycol solution obtained in step (1) was added to a 0.5 nM citrate-modified gold nanosphere solution (average diameter of 45.5 nm). After mixing evenly, the mixture was reacted at 25 °C for 18 h. Through ligand exchange, polyethylene glycol-grafted gold nanospheres (PEG@NPs) with a softness λ of 0.57 were obtained.

[0068] (3) Disperse the polyethylene glycol-grafted gold nanospheres with a softness λ of 0.57 obtained in step (2) into deionized water to prepare a PEG@NPs solution with a concentration of 180 nM.

[0069] (4) Add a 0.50M sodium sulfate aqueous solution to the PEG@NPs solution obtained in step (3) according to a volume ratio of 1:10 between the PEG@NPs solution and the inorganic salt aqueous solution. After mixing evenly, let stand for 3 days to obtain a two-dimensional ordered nano-superlattice material.

[0070] As demonstrated in the above embodiments, when the flexibility λ of the polyethylene glycol-grafted gold nanospheres is controlled to be 0.57, the hydration level of water-soluble polyethylene glycol can be precisely controlled by changing the salt ion concentration, thereby driving the nanoparticles to assemble into a nanocrystalline superlattice with controllable dimensions and morphology. When the salt ion concentration is increased, carbonate ions can largely disrupt the hydrogen bonds between polyethylene glycol and hydrated water molecules, thus driving the assembly into a three-dimensional ordered nanocrystalline superlattice under the strong hydrophobic interaction between the polyethylene glycol molecular chains. When the salt solution concentration is decreased, the ability of carbonate ions to disrupt the hydrogen bonds between polyethylene glycol and hydrated water molecules weakens, meaning the hydration level of polyethylene glycol increases, making the nanoparticles more inclined to assemble into a two-dimensional monolayer superlattice.

Claims

1. A controllable preparation method for a nanoscale superlattice material, characterized in that: First, polyethylene glycol-grafted gold nanospheres with a flexibility λ of 0.57 were dispersed in deionized water to prepare a PEG@NPs solution. Then, an inorganic salt aqueous solution was added to the PEG@NPs solution, and after mixing evenly, the mixture was allowed to stand to obtain a nano-superlattice material. When the concentration of the inorganic salt aqueous solution is 0.60~0.70 M, the nano-superlattice material is a three-dimensional ordered nanocrystalline superlattice material; When the concentration of the inorganic salt aqueous solution is 0.50~0.55 M, the nano-superlattice material is a two-dimensional ordered nanocrystalline superlattice material; The inorganic salt is a soluble carbonate or a soluble sulfate; The softness λ is defined as: ； Where R0 is the mean square end-to-end distance of the polyethylene glycol molecular chain. b is the length of the polyethylene glycol Kuhn segment, with a value of 12 Å, N is the number of polyethylene glycol Kuhn segments, and R c Let be the radius of the gold nanosphere.

2. The controllable preparation method of a nanoscale superlattice material according to claim 1, characterized in that, The resting time is 3 days.

3. The controllable preparation method of a nanoscale superlattice material according to claim 1, characterized in that, The concentration of the PEG@NPs solution is 150~200 nM.

4. The controllable preparation method of a nanoscale superlattice material according to claim 1, characterized in that, The volume ratio of PEG@NPs solution to inorganic salt aqueous solution is 1:

10.

5. The controllable preparation method of a nanoscale superlattice material according to claim 1, characterized in that, Soluble carbonates are potassium carbonate, sodium carbonate, or ammonium carbonate, and soluble sulfates are potassium sulfate, sodium sulfate, ammonium sulfate, or magnesium sulfate.

6. The controllable preparation method of a nanoscale superlattice material according to claim 1, characterized in that, The preparation method of polyethylene glycol-grafted gold nanospheres is as follows: a solution of thiol-modified polyethylene glycol is added to a solution of citrate-modified gold nanospheres, mixed evenly, and reacted at room temperature for 12-24 h. Polyethylene glycol-grafted gold nanospheres are obtained through ligand exchange.

7. The controllable preparation method of a nanoscale superlattice material according to claim 6, characterized in that, The concentration of the thiol-modified polyethylene glycol solution was 1.0–2.0 mM, and the concentration of the citrate-modified gold nanosphere solution was 0.5–5.0 nM.

8. The controllable preparation method of a nanoscale superlattice material according to claim 6, characterized in that, The molar ratio of thiol-modified polyethylene glycol to citrate-modified gold nanospheres is 3000~10000:

1.

9. The controllable preparation method of a nanoscale superlattice material according to claim 6, characterized in that, The number average molecular weight of thiol-modified polyethylene glycol is 1000~10000.

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