Atomic precise metal cluster containing bound positive and negative ion pairs and water-phase synthesis method of atomic precise metal cluster

Abstract

The invention provides an atom precise metal cluster containing bound positive and negative ion pairs and a water-phase synthesis method thereof. The aqueous phase synthesis method comprises the following steps: performing first mixing on a metal precursor aqueous solution and a ligand aqueous solution, supplementing water to obtain an initial solution, and performing second mixing; then adding a reducing agent aqueous solution to obtain a reaction mixed solution; and stirring the reaction mixed solution to obtain the precise atomic metal cluster containing bound positive and negative ion pairs. According to the invention, the cluster is protected by using the bound tight ion pair, so that the cluster core can stably exist in a long time, and the metal cluster with uniform size and precise atoms and with the same molecular weight can be directly obtained, so that the post-treatment step can be simplified, and the feasibility of product amplification and application can be enhanced. In addition, water is used as a unique solvent, so that the generation of waste liquid is reduced.

Description

Technical Field

[0001] This invention belongs to the field of wet chemical synthesis, specifically relating to an atomically precise metal cluster containing bound positive and negative ion pairs and its aqueous phase synthesis method. Background Technology

[0002] The latest generation of active metal phases is metal clusters. Due to their unique electronic structure and unusual physical and chemical properties, ultra-small metal nanoclusters with precise atomic arrangements have broad application prospects in many fields such as catalysis, chemical sensing, electronics, biolabeling, and biomedicine. Currently, progress has been made in the synthesis, separation, purification, characterization, and application research of metal nanoclusters. The technical solution disclosed in CN116727660A involves dissolving chloroauric acid in ethanol, adding mercaptothiophene dropwise, stirring the reaction, filtering, washing, and drying to obtain the gold sulfide precursor Au(tht)Cl; the gold sulfide precursor Au(tht)Cl, a thiol ligand, and triethylamine are fully dispersed in a polar solvent, sodium borohydride is added, and the reaction is stirred to obtain water-soluble gold nanoclusters; however, this method uses organic solvents such as ethanol, generating a large amount of organic waste liquid.

[0003] The technical solution disclosed in CN117531994A involves dissolving silver salt in an organic solvent; simultaneously adding a certain amount of oxidizing metal salt and phosphorus ligand; stirring the solution at room temperature for a period of time to obtain solution A; dissolving a certain amount of reducing agent in an organic solvent and adding it to the aforementioned solution A to obtain solution B; drying solution B by rotary evaporation to obtain solid C; washing solid C with a large amount of organic solvent and centrifuging to obtain solution D; and using a poorly diffusing solvent in solution D to grow colorless and transparent single crystals over a period of time, which are binuclear silver nanoclusters. However, the use of organic solvents generates a large amount of organic waste liquid; the products are mostly dispersed and require crystallization to separate clusters of a single size.

[0004] The technical solution disclosed in CN114197053A involves Au coordinated with phenylethyl mercaptan. 25 The solution is dissolved in an organic solvent; after the Cd salt is dissolved, it is added to the aforementioned solvent along with 2,4-dimethylthiophenol; the solution is heated at a constant temperature of 50-100℃ and stirred for 10-60 minutes to obtain a reddish-brown solution A; the reaction of the reddish-brown solution A is quenched by adding a poor solvent, and the product is centrifuged and repeatedly washed to remove excess thiols and other impurities to obtain a reddish-brown precipitate B; the reddish-brown precipitate B is dissolved in an organic solvent, and pale yellow transparent single crystals and red single crystals grow within 2-3 days. The red single crystal is Au, which has been reported before. 19 Cd3 clusters, pale yellow transparent single crystals, are the newly prepared Au4Cd4 alloy nanoclusters; however, the use of organic solvents generates a large amount of organic waste liquid; the product processing steps are cumbersome and the yield is low; the products are mostly dispersed, requiring complex crystallization methods to separate the target clusters.

[0005] The technical solution disclosed in CN114525125A disperses silver salt and mercapto ligand in a polar solvent and performs ultrasonic treatment. During the ultrasonic treatment, an alkaline solution is added to the mixture to obtain an Ag6 solution. The Ag6 solution is then filtered, allowed to stand, and allowed to evaporate naturally at room temperature to obtain Ag6 nanocluster crystals. However, the polar solvents used are mostly aqueous solutions of methanol, ethanol, acetonitrile, etc., which generate a large amount of organic waste liquid. The product yield is low, and crystallization is required to separate the target product.

[0006] The technical solution disclosed in CN115044051A involves dissolving the ligand levonorgestrel in dichloromethane (DCM), stirring at room temperature until the solution is clear, adding a methanol solution of chloroplatinic acid, and stirring at room temperature; then adding triethylamine and continuing stirring at room temperature; finally adding tetrahydrothiophene gold chloride and stirring at room temperature. After the reaction is complete, the clear solution is allowed to evaporate in the dark at room temperature to obtain crystals, which are then filtered, washed, and air-dried at room temperature. However, the use of highly toxic solvents such as dichloromethane generates a large amount of difficult-to-treat waste liquid; the post-processing of the product is complex, the yield is low, the cluster stability is insufficient, and the fluorescence intensity decreases significantly over time.

[0007] The technical solution disclosed in CN117696882A involves adding a gold source solution and a copper source to a round-bottom flask containing methanol, stirring and dispersing them evenly to obtain a yellow turbid liquid. The mixture is stirred at room temperature, and then bis(diphenylphosphine)methane and adamantine sulfonic acid are added. After 20 minutes, a reducing agent is added to the turbid liquid, and the solution gradually darkens. The reaction is then stirred at room temperature for 8 hours, followed by evaporation to obtain the solution. After purification and separation, gold-copper bimetallic nanoclusters are obtained. However, the use of methanol as a solvent generates a large amount of organic waste liquid; the reaction time is several hours, resulting in low efficiency; and the product requires separation and purification, leading to a low yield.

[0008] The technical solution disclosed in CN117182064A involves dissolving sublimed sulfur in oleylamine to obtain a sulfur precursor solution; adding oleic acid to octadecene, heating to 50°C, adding a copper source, raising the temperature to 165°C, maintaining for 30 min, then lowering the temperature to 105°C, immediately adding the sulfur precursor solution, reacting for 3 min, then adding it to excess acetone, filtering to obtain a precipitate, washing three times with deionized water to obtain copper nanoclusters; weighing PVP and EDC·HCl and adding them to DMA, stirring to dissolve at room temperature, adding octylamine dropwise, reacting at room temperature for 16 h, removing DMA by rotary evaporation after the reaction, dissolving in acetone, adding deionized water, filtering to obtain a solid, washing three times with deionized water, adding ethyl acetate, heating in a 50°C water bath until the solid dissolves, adding dimethylaluminum chloride and stirring, separating and collecting the upper liquid, adding hydrochloric acid, filtering to obtain a solid, and washing with deionized water... The copper nanoclusters were washed three times with water, dissolved in anhydrous ethanol, and evaporated to dryness at 65°C to obtain a white solid. The copper nanoclusters and the white solid were weighed out in proportion and dissolved separately in DCM, denoted as solution A and solution B. Solution A was added dropwise to solution B, mixed thoroughly, and evaporated to dryness at 50°C. The resulting solid was completely dissolved in pH 9.0 borate buffer and concentrated using a 50 kDa ultrafiltration tube to obtain carboxylated copper nanoclusters. The carboxylated copper nanoclusters, along with EDC and PEG, were added to pH 7.4 borate buffer in proportion, completely dissolved, and reacted for 1 hour. The reaction was terminated by adding an equal volume of pH 8.4 borate buffer. The mixture was then concentrated using a 50 kDa ultrafiltration tube to obtain aminated ultrasmall copper nanoclusters. However, the preparation process is extremely cumbersome and inefficient, generating a large amount of organic waste liquid.

[0009] As can be seen from the above existing technologies, the current methods for preparing metal clusters have the following limitations: (1) The main solvents used are still organic solvents, which easily generate a large amount of organic waste liquid; (2) There is insufficient research on the controllable loading of surface protection ligands that are crucial to their stability, especially the lack of research on tightly bound ion pairs, resulting in low cluster stability; and (3) There are problems with uneven size of the initial products of the clusters and difficulty in separation and purification. There is still great room for development in controlling the size that has a profound impact on their physicochemical properties.

[0010] Therefore, it is currently necessary to solve the above problems and provide a method for preparing atomically precise clusters with higher stability and uniform size. Summary of the Invention

[0011] To address the aforementioned technical problems, the present invention aims to provide an atomically precise metal cluster containing bound positive and negative ion pairs and its aqueous phase synthesis method. By forming bound positive and negative ion pairs on the metal surface with ligands to protect the metal core, atomically precise metal clusters with accurate molecular weight, uniform size, and stability can be prepared.

[0012] To achieve the above objectives, the present invention provides an aqueous phase synthesis method for atomically precise metal clusters containing bound positive and negative ion pairs, wherein the aqueous phase synthesis method includes:

[0013] (a) After the metal precursor aqueous solution and the ligand aqueous solution are first mixed, water is added to obtain an initial solution and then a second mixing is performed; then, a reducing agent aqueous solution is added to obtain a reaction mixture;

[0014] (b) The reaction mixture is stirred to obtain atomically precise metal clusters containing bound positive and negative ion pairs;

[0015] The volume ratio of the aqueous solution of the metal precursor to the aqueous solution of the ligand is 1:2 to 1:50.

[0016] The volume ratio of the reducing agent aqueous solution to the initial solution is (0.01-0.25):1.

[0017] According to a specific embodiment of the present invention, preferably, the molar concentration of the metal precursor in the aqueous solution of the metal precursor is 1-50 mM, more preferably 2-30 mM, and the molar concentration of the metal precursor is calculated in terms of metal element.

[0018] According to a specific embodiment of the present invention, preferably, the volume ratio of the aqueous metal precursor solution to the initial solution is 1:30 to 1:130.

[0019] According to a specific embodiment of the present invention, preferably, the metal precursor comprises one or more salts of platinum, palladium, and nickel. More preferably, the metal precursor comprises one or more combinations of chloroplatinic acid, tetraammineplatinum nitrate, platinum nitrate, palladium nitrate, palladium chloride, nickel chloride, and nickel nitrate.

[0020] In some specific embodiments, preferably, the aqueous solution of the metal precursor is obtained by dissolving the metal precursor in water at 0-60°C and mixing it at 0-50°C for 10-120 minutes; more preferably, the aqueous solution of the metal precursor is obtained by dissolving the metal precursor in water at 0-50°C and mixing it at 5-45°C for 10-100 minutes.

[0021] According to a specific embodiment of the present invention, preferably, the molar concentration of the ligand in the aqueous solution of the ligand is 10-500 mM, more preferably 20-300 mM.

[0022] According to a specific embodiment of the present invention, preferably, the ligand comprises one or a combination of two or more of hexadecyltrimethylammonium halide, tetradecyltrimethylammonium halide, dodecyltrimethylammonium halide, and decadecyltrimethylammonium halide; wherein the halogen element comprises any one of bromine, iodine, and chlorine.

[0023] In some specific embodiments, preferably, the ligand aqueous solution is obtained by dissolving the ligand in water at 0-80°C and cooling it to 0-30°C; more preferably, the ligand aqueous solution is obtained by dissolving the ligand in water at 0-60°C and cooling it to 0-20°C.

[0024] Unlike existing technologies, the ligands in this invention do not undergo complete hydrolysis. Only some ligands generate individual positive and negative ions, while the remaining ligands maintain a tightly bound state of positive and negative ions, forming a tightly bound positive and negative ion pair to protect the metal core. Through the study of controllable loading and stacking of ligands on the metal surface, the stability of the metal cluster is enhanced.

[0025] In some specific embodiments, preferably, the volume ratio of the aqueous solution of the metal precursor to the aqueous solution of the ligand is 1:5 to 1:40; more preferably, 1:5 to 1:20; and even more preferably, 1:10 to 1:20.

[0026] In some specific embodiments, preferably, the amount of the reducing agent aqueous solution added is 1.25 vol% - 20 vol%, based on the volume of the initial solution being 100%.

[0027] According to a specific embodiment of the present invention, preferably, the molar concentration of the reducing agent in the aqueous reducing agent solution is 1-50 mM, more preferably 5-40 mM.

[0028] According to a specific embodiment of the present invention, preferably, the reducing agent includes one or a combination of two or more of hydrazine hydrate, sodium borohydride, ascorbic acid, and potassium borohydride.

[0029] In some specific embodiments, preferably, the reducing agent aqueous solution is obtained by dissolving the reducing agent in water at 0-60°C; more preferably, the reducing agent aqueous solution is obtained by dissolving the reducing agent in water at 0-40°C.

[0030] According to a specific embodiment of the present invention, preferably, the temperature of the first mixture is -5°C to 20°C, more preferably -5°C to 15°C.

[0031] In some specific embodiments, preferably, the volume of the initial solution is 20-50 mL, more preferably 20-40 mL, and the temperature of the added water is the same as the temperature of the solution during the first mixing.

[0032] According to a specific embodiment of the present invention, preferably, the second mixing condition is to stir and mix at a temperature of -5°C to 60°C for 1-10 minutes; more preferably, the second mixing condition is to stir and mix at a temperature of -5°C to 50°C for 2-10 minutes.

[0033] According to a specific embodiment of the present invention, preferably, the operation of adding the reducing agent aqueous solution is to add the reducing agent aqueous solution within a time of 1-20s (preferably 1-10s) under magnetic stirring at 200-1000rpm.

[0034] In some specific embodiments, preferably, the volume of the reducing agent aqueous solution is 0.5-5 mL; more preferably, it is 0.5-4 mL.

[0035] According to a specific embodiment of the present invention, preferably, in step (b), the stirring speed is 100-1000 rpm (preferably 200-1000 rpm), the stirring temperature is -5℃ to 60℃ (preferably -5℃ to 50℃), and the stirring time is 1 min to 24 h (preferably 1 min to 12 h).

[0036] The present invention also provides an atomically precise metal cluster containing bound positive and negative ion pairs, which is prepared by the above-described aqueous synthesis method.

[0037] According to a specific embodiment of the present invention, preferably, the number of metal atoms in the core of a single atom-precise metal cluster is 5-150; the ratio of the number of metal atoms to the number of bound positive and negative ion pairs is 1:10 to 10:1 (preferably 1:5 to 5:1).

[0038] In this invention, the prepared metal clusters are atomically precise clusters with bound positive and negative ion pairs protecting their surfaces. These atomically precise clusters refer to macromolecules with precise molecular weights, aperiodic arrangement, perfectly uniform size, and containing a metal core and surface ligands (i.e., bound positive and negative ion pairs). This invention achieves rapid formation of uniformly sized cluster products (e.g., clusters all 1 nm in size) by controlling reaction temperature and other conditions; and further improves the size uniformity and stability of the metal clusters by introducing tightly bound ion pairs on the cluster surface to protect the metal core, thereby obtaining atomically precise and stable metal clusters.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) The aqueous synthesis method of atomically precise metal clusters containing bound positive and negative ion pairs provided by the present invention uses water as the only solvent, rather than organic solvents such as methanol, ethanol, and acetonitrile, thereby reducing the generation of waste liquid, lowering the cost of waste treatment, and reducing the environmental pressure on subsequent production scale-up and industrial applications.

[0041] (2) The atomically precise metal clusters provided by the present invention use tightly bound ion pairs to protect the clusters and apply appropriate constraints so that the cluster core can exist stably for a long time; at the same time, the modification can also be achieved through the ability of rapid replacement of ion pairs.

[0042] (3) The aqueous synthesis method for atomically precise metal clusters containing bound positive and negative ion pairs provided by this invention uses tightly bound ion pairs to protect the clusters, which can directly obtain metal clusters with uniform size and atomic precision and the same molecular weight. Therefore, it can greatly simplify the post-processing steps and enhance the feasibility of product scale-up and application. In addition, since the aqueous synthesis method provided by this invention produces a single and precise product, the cluster yield is close to 100% provided that a sufficient amount of reducing agent is provided, which greatly solves the problem of low yield. Attached Figure Description

[0043] Figure 1 Transmission electron microscopy image of the atomically precise clusters prepared in Example 1.

[0044] Figure 2 The image shows the MALDI-TofMS mass spectrum of the atomically precise clusters prepared in Example 1.

[0045] Figure 3 The absorption curves are for the atomically precise clusters prepared in Example 1.

[0046] Figure 4 The three-dimensional theoretical structure diagram of the metal core in the atomically precise cluster prepared in Example 1 (left side) and the corresponding high-resolution transmission electron microscope (HRTEM) image (right side).

[0047] Figure 5 The image shows the three-dimensional theoretical structure of the metal core in the atomically precise cluster prepared in Example 2 (left image) and the corresponding high-resolution transmission electron microscopy (HRTEM) image (right image).

[0048] Figure 6 Three-dimensional theoretical structural diagrams of the atomically precise clusters prepared in Examples 1 (left), 2 (middle), and 3 (right).

[0049] Figure 7 TEM image of the platinum nanoparticle sol prepared in Comparative Example 1.

[0050] Figure 8This is a TEM image of the palladium nanoparticle sol prepared in Comparative Example 2.

[0051] Figure 9 This is a TEM image of the nickel nanoparticle sol prepared in Comparative Example 3.

[0052] Figure 10 The MALDI-TofMS mass spectra of the atomically precise clusters prepared in Example 1 at the beginning of ligand exchange (top panel) and after ligand exchange is completed (bottom panel).

[0053] Figure 11 Dark-field image of atomically precise clusters prepared in living biological cells, as shown in Example 1. Detailed Implementation

[0054] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0055] Example 1:

[0056] This embodiment provides an aqueous phase synthesis method for atomically precise metal clusters containing bound positive and negative ion pairs, specifically including the following steps:

[0057] (1) Preparation of precursor solution: Dissolve the metal salt in water at 10°C and mix at 10°C for 10 minutes to prepare a metal precursor solution; wherein the metal salt is chloroplatinic acid and the total molar concentration of the metal salt in water is 10 mM by molar amount.

[0058] (2) Preparation of ligand solution: The ligand is dissolved in water at 10°C, and the solution is cooled to 5°C. The ligand is hexadecyltrimethylammonium bromide, and the total molar concentration of the ligand in water is 200 mM by molar amount.

[0059] (3) Preparation of reducing agent solution: Dissolve the reducing agent in water at 0℃. The reducing agent is sodium borohydride. The total molar concentration of the reducing agent in water is 10mM by molar amount.

[0060] (4) Reduction of precursor: 0.625 mL of precursor solution and 6.25 mL of ligand solution were mixed at 10 °C, and water at the same temperature was added to a total volume of 23.5 mL to obtain an initial solution. The solution was stirred at 10 °C for 1 minute. Then, 1.5 mL of reducing agent solution was added within 1 second under magnetic stirring at 1000 rpm to obtain a reaction mixture.

[0061] (5) Loading of bound positive and negative ion pairs: The reaction mixture was stirred at 1000 rpm for 1 min to obtain a solution containing atomically precise metal clusters containing bound positive and negative ion pairs; wherein the cluster surface contains metal clusters protected by bound positive and negative ion pairs, and for a single cluster, the number of metal atoms in the cluster core is 32, and the ratio of the number of metal cluster atoms to the number of bound positive and negative ion pairs is 8:5, denoted as Pt 32 (CTA + ·Br - ) 20 Atomic precision clusters.

[0062] The Pt 32 (CTA + ·Br - ) 20 Transmission electron microscopy images of precise atomic clusters, such as Figure 1 As shown, from Figure 1 As can be seen from this, all Pt 32 (CTA + ·Br - ) 20 Atom-precise clusters have exactly the same single precise size.

[0063] In this embodiment, Pt contains bound positive and negative ion pairs. 32 (CTA + ·Br - ) 20 The atomically precise cluster has 32 Pt atomic cores and 20 CTA atoms. + Cation (hexadecyltrimethylammonium cation) and 20 Br - The bound ion pairs formed by anions (CTA) + ·Br - The MALDI-TofMS mass spectrometry results for this atomically precise cluster are as follows: Figure 2 As shown, from Figure 2 As can be seen from the data, the main peak is 13531 Da, which indicates that all Pt... 32 (CTA + ·Br - ) 20 The atomically precise clusters have the same molecular weight, and the left-hand side peak at 13167 Da differs from the main peak by one CTA. + ·Br - The mass of the bound positive and negative ion pairs.

[0064] Furthermore, Pt containing bound positive and negative ion pairs 32 (CTA + ·Br - ) 20 Absorption curves of precise atomic clusters are as follows Figure 3As shown, from Figure 3 As can be seen, this cluster has obvious absorption peaks, indicating that it has molecular characteristics.

[0065] Example 2:

[0066] This embodiment provides an aqueous phase synthesis method for atomically precise metal clusters containing bound positive and negative ion pairs, specifically including the following steps:

[0067] (1) Preparation of precursor solution: Dissolve the metal salt in water at 5°C and mix at 5°C for 10 minutes to prepare a metal precursor solution. The metal salt is palladium chloride, and the total molar concentration of the metal salt in water is 10 mM by molar amount.

[0068] (2) Preparation of ligand solution: The ligand was dissolved in water at 5°C and cooled to 3°C after forming a solution. The ligand was tetradecyltrimethylammonium bromide and the total molar concentration of the ligand in water was 200 mM by molar amount.

[0069] (3) Preparation of reducing agent solution: Dissolve the reducing agent in water at 0℃. The reducing agent is sodium borohydride. The total molar concentration of the reducing agent in water is 10mM by molar amount.

[0070] (4) Reduction of precursor: 0.625 mL of precursor solution and 3.125 mL of ligand solution were mixed at 5 °C, and water at the same temperature was added to a total volume of 28.5 mL to obtain an initial solution. The solution was stirred at 5 °C for 1 minute. Then, 1.5 mL of reducing agent solution was added within 1 second under magnetic stirring at 1000 rpm to obtain a reaction mixture.

[0071] (5) Loading of bound positive and negative ion pairs: The reaction mixture was stirred at 1000 rpm for 30 min to obtain a solution containing atomically precise metal clusters with bound positive and negative ion pairs. The cluster surface contained metal clusters protected by bound positive and negative ion pairs. For a single cluster, the number of metal atoms in the cluster core was 25, and the ratio of the number of metal cluster atoms to the number of bound positive and negative ion pairs was 25:18, denoted as Pd. 25 (MTA + ·Br - ) 18 Atomic precision clusters, MTA + It is a tetradecyltrimethylammonium bromide cation.

[0072] Example 3:

[0073] This embodiment provides an aqueous phase synthesis method for atomically precise metal clusters containing bound positive and negative ion pairs, specifically including the following steps:

[0074] (1) Preparation of precursor solution: Dissolve the metal salt in water at 15°C and mix at 15°C for 10 minutes to prepare a metal precursor solution. The metal salt is nickel nitrate and the total molar concentration of the metal salt in water is 10 mM by molar amount.

[0075] (2) Preparation of ligand solution: The ligand was dissolved in water at 15°C and cooled to 10°C after forming a solution. The ligand was dodecyltrimethylammonium bromide and the total molar concentration of the ligand in water was 200 mM by molar amount.

[0076] (3) Preparation of reducing agent solution: Dissolve the reducing agent in water at 0℃. The reducing agent is sodium borohydride. The total molar concentration of the reducing agent in water is 10mM by molar amount.

[0077] (4) Reduction of precursor: 0.313 mL of precursor solution and 6.25 mL of ligand solution were mixed at 15 °C, and water at the same temperature was added to a total volume of 38.5 mL to obtain an initial solution. The solution was stirred at 15 °C for 1 hour. Then, 1.5 mL of reducing agent solution was added in 1 second under magnetic stirring at 1000 rpm to obtain a reaction mixture.

[0078] (5) Loading of bound positive and negative ion pairs. The reaction mixture was stirred at 500 rpm for 30 min to obtain a solution containing atomically precise metal clusters containing bound positive and negative ion pairs. The cluster surface contained metal clusters protected by bound positive and negative ion pairs. For a single cluster, the number of metal atoms in the cluster core was 102, and the ratio of the number of metal cluster atoms to the number of bound positive and negative ion pairs was 51:22, expressed as Ni. 102 (DTA + ·Br - ) 44 Atomic Precision Clusters, DTA + It is a dodecyltrimethylammonium bromide cation.

[0079] Comparative Example 1:

[0080] This comparative example provides a method for preparing nanoparticle sol, specifically including the following steps:

[0081] (1) Weigh a certain amount of chloroplatinic acid powder, dissolve it in double-distilled water, prepare a 2g / L chloroplatinic acid aqueous solution, place it in a brown bottle and store it in a refrigerator at 4℃ for later use.

[0082] (2) Weigh a certain amount of gelatin and dissolve it in double-distilled water under heating conditions to prepare a 25g / L gelatin aqueous solution. Cool it for later use.

[0083] (3) Mix the above chloroplatinic acid solution and gelatin solution at a volume ratio of 1:1 and stir for 10 min. After the mixture is fully mixed, add hydrazine hydrate solution (concentration of 30%) twice the amount of chloroplatinic acid to the mixture and stir continuously for 60 min to obtain nano-platinum particle sol.

[0084] Comparative Example 2:

[0085] This comparative example provides a method for preparing nanoparticle sol, specifically including the following steps:

[0086] (1) Weigh a certain amount of palladium chloride powder, dissolve it in double-distilled water, prepare a 2g / L palladium chloride aqueous solution, place it in a brown bottle and store it in a refrigerator at 4℃ for later use.

[0087] (2) Weigh a certain amount of gelatin and dissolve it in double-distilled water under heating conditions to prepare a 25g / L gelatin aqueous solution. Cool it for later use.

[0088] (3) Mix the above palladium chloride solution and gelatin solution at a volume ratio of 1:1.2 and stir for 10 min. After the mixture is fully mixed, add hydrazine hydrate solution (concentration of 30%) twice the amount of palladium chloride to the mixture and stir continuously for 60 min to obtain nano-palladium particle sol.

[0089] Comparative Example 3:

[0090] This comparative example provides a method for preparing nanoparticle sol, specifically including the following steps:

[0091] (1) Weigh a certain amount of nickel nitrate powder, dissolve it in double-distilled water, prepare a 2g / L nickel nitrate aqueous solution, place it in a brown bottle and store it in a refrigerator at 4℃ for later use.

[0092] (2) Weigh a certain amount of gelatin and dissolve it in double-distilled water under heating conditions to prepare a 25g / L gelatin aqueous solution. Cool it for later use.

[0093] (3) Mix the above nickel nitrate solution and gelatin solution at a volume ratio of 1:1 and stir for 10 min. After the mixture is fully mixed, add hydrazine hydrate solution (concentration of 30%) twice the amount of nickel nitrate to the mixture and stir continuously for 60 min to obtain nano-nickel particle sol.

[0094] The microstructures of the atomically precise clusters prepared in Examples 1-3 and the metal particle sols prepared in Comparative Examples 1-3 are investigated below, with specific analysis as follows:

[0095] In Example 1, Pt 32 (CTA + ·Br - )20 The three-dimensional theoretical structure diagram of the metallic core of a precise atomic cluster is shown below. Figure 4 The left-hand image shows the blue spheres representing Pt atoms; the corresponding high-resolution transmission electron microscopy (HRTEM) images are shown below. Figure 4 As shown in the right-hand image, the width of the HRTEM image is 1 nm, and the size of the cluster is about 0.9 nm. It can be seen that the internal atomic sites show a lack of periodicity in the structure.

[0096] Pd in ​​Example 2 25 (MTA + ·Br - ) 18 The three-dimensional theoretical structure diagram of the metallic core of a precise atomic cluster is shown below. Figure 5 The left-hand image shows the red spheres representing Pd atoms; the corresponding high-resolution transmission electron microscopy (HRTEM) images are shown below. Figure 5 As shown in the right-hand image, the width of the HRTEM image is 1 nm, and the size of the cluster is about 0.9 nm. It can be seen that the internal atomic sites show a lack of periodicity in the structure.

[0097] Accordingly, the Pt containing bound positive and negative ion pairs prepared in Examples 1-3 32 (CTA + ·Br - ) 20 Pd 25 (MTA + ·Br - ) 18 Ni 102 (DTA + ·Br - ) 44 The three-dimensional theoretical structure diagram of precise atomic clusters is shown below. Figure 6 As shown, all gray spheres represent bound positive and negative ion pairs, while blue spheres represent Pt atoms (left figure, Example 1), red spheres represent Pd atoms (middle figure, Example 2), and black spheres represent Ni atoms (right figure, Example 3).

[0098] In contrast, the TEM images of the nano-metal particle sols prepared in Comparative Examples 1, 2, and 3 are as follows: Figure 7 , Figure 8 , Figure 9 As shown, the width of each of the three TEM images corresponds to 2nm; however, Figure 7-9 The internal atomic arrangement in the nanoparticles exhibits a clear periodicity. Therefore, the nanoparticle sols prepared in Comparative Examples 1-3 are large nanoparticles, and atomically precise clusters were not successfully prepared.

[0099] The following describes Pt in Example 1. 32 (CTA +·Br - ) 20 The ligand substitution ability of precise atomic clusters was investigated, and the specific results are as follows:

[0100] In (PTA) + ·Br - In the solution, Pt in Example 1 32 (CTA + ·Br - ) 20 When the precise atomic clusters begin ligand substitution 15 seconds later, different amounts of (CTA) are lost. + ·Br - The MALDI-Tof MS mass spectrometry results after binding the positive and negative ion pairs are as follows: Figure 10 As shown in the upper figure, among the series of peaks formed, peak 12803 is Pt. 32 (CTA + ·Br - ) 20 Two lost (CTA) + ·Br - The signal that follows the binding of positive and negative ion pairs.

[0101] Furthermore, Pt 32 (CTA + ·Br - ) 20 MALDI-Tof MS mass spectrometry results of atomically precise clusters after ligand exchange are as follows: Figure 10 As shown in the lower diagram, from Figure 10 As can be seen in the lower image, Pt 32 (CTA + ·Br - ) 20 Atomic Precision Cluster Input (PTA) + ·Br - After three minutes in the solution, Pt 32 (CTA + ·Br - ) 20 (CTA) of atomically precise cluster surfaces + ·Br - The bound positive and negative ion pairs can be rapidly replaced by (PTA) + ·Br - ) Bound positive and negative ion pairs, of which PTA + The cation is pentadecyltrimethylammonium bromide, which causes the corresponding cluster to also become Pd. 32 (PTA + ·Br - ) 20 Series clusters, and Pd within them32 The core remains unchanged; only the bound positive and negative ion pairs on the surface undergo rapid replacement.

[0102] Therefore, the above results demonstrate that precisely defined atomic clusters protected by bound positive and negative ion pairs can undergo flexible surface ligand substitution.

[0103] The following describes Pt in Example 1. 32 (CTA + ·Br - ) 20 The stability of precise atomic clusters was investigated, and the specific results are as follows:

[0104] In Example 1, Pt 32 (CTA + ·Br - ) 20 Dark-field images of precise atomic clusters in living biological cells, such as Figure 11 As shown in the figure, the brightness indicates the binding of metal clusters to cell surface targets. Figure 11 As can be seen from Pt 32 (CTA + ·Br - ) 20 Atomic precision clusters have good stability and can be used as reliable optical pointers for drug delivery and disease diagnosis.

Claims

1. An aqueous phase synthesis method for atomically precise metal clusters containing bound positive and negative ion pairs, wherein, The aqueous phase synthesis method includes: (a) After the metal precursor aqueous solution and the ligand aqueous solution are first mixed, water is added to obtain an initial solution and then a second mixing is performed; then, a reducing agent aqueous solution is added to obtain a reaction mixture; (b) The reaction mixture is stirred to obtain atomically precise metal clusters containing bound positive and negative ion pairs; The volume ratio of the aqueous solution of the metal precursor to the aqueous solution of the ligand is 1:2 to 1:

50. The volume ratio of the reducing agent aqueous solution to the initial solution is (0.01-0.25):

1.

2. The aqueous phase synthesis method according to claim 1, wherein, In the aqueous solution of the metal precursor, the molar concentration of the metal precursor is 1-50 mM, and the molar concentration of the metal precursor is calculated in terms of metal element.

3. The aqueous phase synthesis method according to claim 1, wherein, The volume ratio of the aqueous solution of the metal precursor to the initial solution is 1:30 to 1:

130.

4. The aqueous phase synthesis method according to claim 1 or 2, wherein, The metal precursor includes one or more of the salts of platinum, palladium, and nickel.

5. The aqueous phase synthesis method according to claim 4, wherein, The metal precursor includes one or more of the following: chloroplatinic acid, tetraammineplatinum nitrate, platinum nitrate, palladium nitrate, palladium chloride, nickel chloride, and nickel nitrate.

6. The aqueous phase synthesis method according to claim 1, wherein, In the aqueous solution of the ligand, the molar concentration of the ligand is 10-500 mM.

7. The aqueous phase synthesis method according to claim 1 or 6, wherein, The ligands include one or more of hexadecyltrimethylammonium halide, tetradecyltrimethylammonium halide, dodecyltrimethylammonium halide, and decadecyltrimethylammonium halide; Halogens include any one of bromine, iodine, and chlorine.

8. The aqueous phase synthesis method according to claim 1, wherein, In the aqueous solution of the reducing agent, the molar concentration of the reducing agent is 1-50 mM.

9. The aqueous phase synthesis method according to claim 1 or 8, wherein, The reducing agent includes one or a combination of two or more of hydrazine hydrate, sodium borohydride, ascorbic acid, and potassium borohydride.

10. The aqueous phase synthesis method according to claim 1, wherein, The temperature of the first mixture is -5°C to 20°C; And / or, the second mixing condition is to stir and mix at a temperature of -5°C to 60°C for 1-10 minutes; And / or, the operation of adding the reducing agent aqueous solution is to add the reducing agent aqueous solution within 1-20 seconds under magnetic stirring at 200-1000 rpm.

11. The aqueous phase synthesis method according to claim 1, wherein, In step (b), the stirring speed is 100-1000 rpm, the stirring temperature is -5℃ to 60℃, and the stirring time is 1 min to 24 h.

12. An atomically precise metal cluster containing bound positive and negative ion pairs, which is prepared by the aqueous phase synthesis method according to any one of claims 1-11.

13. The atomically precise metal cluster according to claim 12, wherein, The number of metal atoms in the core of a single atom-precise metal cluster is 5-150; the ratio of the number of metal atoms to the number of bound positive and negative ion pairs is 1:10 to 10:1.

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