Water-soluble gold nanoclusters with crystallographic structure and preparation method thereof

Abstract

The application provides a water-soluble gold nanocluster with a crystallographic structure and a preparation method thereof. The water-soluble Au 25 nanocluster with a single crystal structure is synthesized by using 2-mercaptonicotinic acid, 6-mercaptonicotinic acid or 6-mercaptobenzoic acid as a protective ligand, and the single crystal structure of the water-soluble Au 25 nanocluster is determined. The method in the application is simple, the reaction condition is easy to realize, and the gold nanocluster with a single crystal structure is obtained, and the accurate single crystal structure of the gold nanocluster is obtained, which is very important for analyzing the correlation between fluorescence and structure. The gold nanocluster Au 15 (2-Hmna) obtained by the application has near-infrared luminescence, the near-infrared has a deeper penetration into biological tissues, and has great application potential in the biomedical field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanoclusters and coordination chemistry, and particularly relates to a water-soluble gold nanocluster with a crystallographic structure and a preparation method thereof. BACKGROUND

[0002] Water-soluble gold nanoclusters have inherent advantages such as non-toxicity, good biocompatibility, and diverse supramolecular assembly forms, and are expected to make up for the deficiencies of organic soluble coin metal nanoclusters in water phase applications. In the past few decades, a large number of water-soluble coin metal nanoclusters have been prepared by using thiol ligands containing carboxyl groups (glutathione, bovine serum albumin, cysteine, captopril, 11-mercaptohexadecanoic acid, 16-mercaptohexadecanoic acid, 6-mercaptohexanoic acid, mercaptobenzoic acid, etc.), some of which have been applied in sensors and biology. Efforts to elucidate the chemical composition of water-soluble coin metal nanoclusters have been advancing. Mass spectrometry, nuclear magnetic resonance spectroscopy, and time-dependent density functional theory have been used to provide possible structural information.

[0003] However, the development of water-soluble gold nanoclusters is relatively lagging. Despite the many advances, there are insurmountable obstacles in crystallizing water-soluble gold nanoclusters, which may be due to the inherent structural characteristics of the weak ionization properties of -COOH, resulting in a high dependence of the solubility of gold nanoclusters on external factors (temperature, pH, ionic strength, etc.), thus preventing the atomic level separation and revealing the crystal structure of water-soluble gold nanoclusters stabilized by thiol ligands, which seriously hinders the comprehensive study of the relationship between the structure and performance of water-soluble gold nanoclusters. Chinese patent document CN101406961A discloses a gold nanocluster preparation method. The method is as follows: after mixing methanol and Au 3+ compound, then adding an aqueous solution of a mercapto organic compound, and then adding an aqueous solution of NaBH4, to obtain a mixture, centrifugally washing the mixture with an aqueous methanol solution and deionized water, and finally drying the mixture at a drying temperature of 30-70°C and a vacuum degree of 1-10 -3 Pa for 6-18 hours to obtain water-soluble gold nanoclusters. Chinese patent document CN105772742A discloses a preparation method and application of fluorescent gold nanoclusters, which are prepared by mixing 1-8 parts of a 2-mercapto-5-benzimidazole sulfonic acid sodium aqueous solution with a concentration of 5-500 mmol / L and 1-5 parts of a chloroauric acid aqueous solution with a concentration of 5-500 mmol / L, stirring for 1-30 minutes, then adding 1-5 parts of a 0.1-1 mol / L sodium hydroxide aqueous solution, and continuing to stir for 10-50 minutes, and then drying to obtain fluorescent gold nanoclusters. However, the above-mentioned patents cannot obtain gold nanoclusters with a single crystal structure, and the crystal structure thereof is not determined, which seriously limits the study of the structure and the structure-activity relationship of the fluorescent properties of water-soluble gold nanoclusters.

[0004] Therefore, developing a new synthesis strategy, optimizing the synthesis process of water-soluble gold nanoclusters, and optimizing the crystallization process are crucial for the later application of water-soluble gold nanoclusters. SUMMARY

[0005] In view of the problems in the prior art, the application provides a water-soluble gold nanocluster with a crystallographic structure and a preparation method thereof. 25 The application uses 2-mercapto-nicotinic acid, 6-mercapto-nicotinic acid or 6-mercapto-benzoic acid as a protective ligand to synthesize water-soluble Au 25 nanoclusters with a single crystal structure, and determines the single crystal structure thereof. The method in the application is simple, the reaction conditions are easy to realize, and gold nanoclusters with a single crystal structure are obtained, and the accurate single crystal structure thereof is obtained, which is very important for analyzing the correlation between fluorescence and structure. The application has great application potential in the biomedical field.

[0006] The technical scheme of the application is as follows.

[0007] One of the purposes of the application is to provide a water-soluble gold nanocluster with a crystallographic structure, which is a thiol ligand-protected Au 25 nanocluster. The thiol ligand is 2-mercapto-nicotinic acid (2-H2mna), 6-mercapto-nicotinic acid (6-H2mna) or 6-mercapto-benzoic acid (p-mba).

[0008] According to the application, the molecular formula of the gold nanocluster is Au 25 (2-Hmna) 15 , Au 25 (6-Hmna) 18 or Au 25 (p-mba) 18 .

[0009] The second purpose of the application is to provide a preparation method of a water-soluble gold nanocluster with a crystallographic structure, which comprises the following steps.

[0010] (1) Dissolve chloroauric acid in ethanol, add mercaptothiophene dropwise, stir and react, filter, wash and dry to obtain a sulfur gold precursor Au(tht)Cl;

[0011] (2) Disperse the sulfur gold precursor Au(tht)Cl, a thiol ligand and triethylamine in a polar solvent, add sodium borohydride, stir and react to obtain a water-soluble gold nanocluster.

[0012] According to the application, in step (1), the mercaptothiophene is 2-mercaptothiophene or 3-mercaptothiophene.

[0013] According to the application, preferably, in step (1), the molar ratio of chloroauric acid to ethanol is 0.1-0.5 mol / L.

[0014] According to the application, preferably, in step (1), the molar ratio of chloroauric acid to mercaptothiophene is (1:0.2)-(1:1).

[0015] According to the application, preferably, in step (1), the dropping of mercaptothiophene is carried out under stirring.

[0016] According to the application, preferably, in step (1), the stirring reaction temperature is room temperature, and the stirring reaction time is 1-3 h.

[0017] According to the application, preferably, in step (1), the washing is carried out by using ethanol and diethyl ether in sequence.

[0018] According to the application, preferably, in step (2), the thiol ligand is 2-mercaptonicotinic acid (2-H2mna), 6-mercaptonicotinic acid (6-H2mna) or 6-mercaptobenzoic acid (p-mba).

[0019] According to the application, preferably, in step (2), the molar ratio of Au(tht)Cl to the thiol ligand is (1:1)-(1:4).

[0020] According to the application, preferably, in step (2), the molar ratio of Au(tht)Cl to triethylamine is (1:18)-(1:25).

[0021] According to the application, preferably, in step (2), the molar ratio of Au(tht)Cl to sodium borohydride is (1:1)-(1:5).

[0022] According to the application, preferably, in step (2), the polar solvent is water; and the molar ratio of Au(tht)Cl to the polar solvent is 0.001-0.01 mol / L.

[0023] According to the application, preferably, in step (2), the stirring reaction temperature is room temperature, and the stirring reaction time is 10-12 h.

[0024] According to the application, preferably, in step (2), the reaction solution obtained in the reaction is slowly volatilized in a dark environment at room temperature to obtain the water-soluble gold nanoclusters.

[0025] The technical features and beneficial effects of the application are as follows:

[0026] 1. The application uses 2-mercaptonicotinic acid, 6-mercaptonicotinic acid or 6-mercaptobenzoic acid as a protective ligand to synthesize water-soluble Au 25nanoclusters and determined their single crystal structures. It is worth mentioning that 2-mercaptonicotinic acid and 6-mercaptonicotinic acid have never been used as protective ligands in the prior art to synthesize water-soluble Au 25 nanoclusters, although 6-mercaptobenzoic acid has been reported in the prior art, but single crystal structure of the nanoclusters has never been successfully obtained and the crystal structure has never been determined. The present application not only uses 2-mercaptonicotinic acid and 6-mercaptonicotinic acid to obtain two new examples of water-soluble Au 25 nanoclusters with single crystal structure, and accurately determines the single crystal structures of the nanoclusters.

[0027] 2、The method in the present application is simple and the reaction conditions are easy to realize. The present application obtains water-soluble gold nanoclusters with single crystal structure, and accurately determines the single crystal structure, which has never been realized in the prior art, and the crystallographic structure is very important for analyzing the correlation between fluorescence and structure. The gold nanoclusters obtained in the present application have the advantages of high fluorescence intensity, high fluorescence quantum yield, and high water solubility. 25 (2-Hmna) 15 In the near-infrared luminescence, compared with the visible light obtained by the prior art, the near-infrared can penetrate deeper into biological tissues, and can maximize the harm to human tissues, which has great potential in biomedical applications, which has never been realized in the prior art.

[0028] 3、In the preparation method of the present application, the synthesis of sulfur gold precursor Au(tht)Cl is very important. In the preparation process of the sulfur gold precursor Au(tht)Cl in the present application, the addition of mercaptothiophene can reduce Au 3+ to Au + compound, which can shorten the process of reducing Au + to Au 0 by sodium borohydride; it is beneficial to form gold nanoclusters with single crystal structure; if other reagents are used instead, the yield of gold nanoclusters will be reduced, and a mixture of gold nanoclusters with multiple crystal structures will be obtained.

[0029] 4、The thiol ligand used in the present application is a drug intermediate, and the presence of nitrogen atoms on the ligand 2-mercaptonicotinic acid and 6-mercaptonicotinic acid is beneficial to obtain gold nanoclusters with single crystal structure. Triethylamine can further deprotonate the carboxyl group, improve the water solubility of the gold nanoclusters, and be beneficial to obtain gold nanoclusters with single crystal structure in the present application. The ratio of sulfur gold precursor Au(tht)Cl, thiol ligand and triethylamine is crucial for the synthesis of gold nanoclusters with single crystal structure, and if it is not appropriate, a mixture of gold nanoclusters with multiple crystal structures will be obtained. The ratio of raw materials also has a certain influence on the yield of the target product, and if the ratio of raw materials is not appropriate, the yield of the target product will also be reduced. The polar solvent is preferably an aqueous solvent, because the water-soluble gold nanoclusters have better solubility in water. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25 (2-Hmna) 15 Schematic diagram of the overall structure of gold nanoclusters.

[0031] Figure 2 Synthesis of novel water soluble Au prepared for Example 9 of the present invention 25 (6-Hmna) 18 Schematic diagram of the overall structure of gold nanoclusters.

[0032] Figure 3 Synthesis of novel water soluble Au prepared for Example 10 of the present invention 25 (p-mba) 18 Schematic diagram of the overall structure of gold nanoclusters.

[0033] Figure 4 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25 (2-Hmna) 15 Structural dissection of gold nanoclusters and Au reported in the prior art 25 (SR) 18 ; where SR represents a thiol ligand.

[0034] Figure 5 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25 (2-Hmna) 15 Electrospray mass spectrum of gold nanoclusters.

[0035] Figure 6 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25 (2-Hmna) 15 Liquid UV spectrum of gold nanoclusters.

[0036] Figure 7 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25 (2-Hmna) 15 Time monitoring stability plot of liquid UV spectrum of gold nanoclusters.

[0037] Figure 8 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25 (2-Hmna) 15 Liquid near infrared emission plot of gold nanoclusters.

[0038] Figure 9 Synthesis of novel water soluble Au prepared for Example 1 of the present invention 25(2-Hmna) 15 Liquid fluorescence decay lifetime map of gold nanoclusters. DETAILED DESCRIPTION

[0039] The application will be further described in connection with the specific embodiments and drawings, but not limited thereto.

[0040] The raw materials used in the examples are all conventional products unless otherwise specified; the methods used are all prior art unless otherwise specified.

[0041] Example 1:

[0042] A preparation method of a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0043] (1) Synthesis of sulfur gold precursor Au(tht)Cl: 5 mmol of chloroauric acid was dissolved in 20 mL of ethanol, then 3 mmol of mercaptothiophene (3-mercaptothiophene) was added dropwise to the chloroauric acid solution under vigorous stirring, and then the reaction was stirred at room temperature for 1 h. The white snow-like solid was obtained by suction filtration, washed with ethanol and diethyl ether in turn, and dried to obtain Au(tht)Cl.

[0044] (2) Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and was stirred for 10 minutes, 1 mg (0.026 mmol) of reducing agent sodium borohydride was added, and the solution was stirred at room temperature for 10 hours. Then, the solvent was slowly evaporated at room temperature in the dark environment to obtain gold nanoclusters Au 25 (2-Hmna) 15 with a single-step yield of 23%.

[0045] Example 2:

[0046] A preparation method of a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0047] (1) Synthesis of sulfur gold precursor Au(tht)Cl: the method is the same as in Example 1.

[0048] (2) Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and was stirred for 10 minutes, 1 mg (0.026 mmol) of reducing agent sodium borohydride was added, and the solution was stirred at room temperature for 10 hours. Then, the solvent was slowly evaporated at room temperature in the dark environment to obtain gold nanoclusters Au 25 (2-Hmna) 15, single step yield 31%.

[0049] Example 3:

[0050] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0051] (1) Synthesis of sulfur gold precursor Au(tht)Cl: same as example 1.

[0052] (2) Au(tht)Cl (0.02 mmol, 10 mg) and 0.06 mmol of thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and was stirred for 10 minutes, 1 mg (0.026 mmol) of reducing agent sodium borohydride was added, stirred at room temperature for 10 hours, then slowly evaporated at room temperature in the dark environment to obtain gold nanocluster Au 25 (2-Hmna) 15 , single step yield 16%.

[0053] Example 4:

[0054] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0055] (1) Synthesis of sulfur gold precursor Au(tht)Cl: same as example 1.

[0056] (2) Au(tht)Cl (0.02 mmol, 10 mg) and 0.08 mmol of thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and was stirred for 10 minutes, 1 mg (0.026 mmol) of reducing agent sodium borohydride was added, stirred at room temperature for 10 hours, then slowly evaporated at room temperature in the dark environment to obtain gold nanocluster Au 25 (2-Hmna) 15 , single step yield 11%.

[0057] Example 5:

[0058] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0059] (1) Synthesis of sulfur gold precursor Au(tht)Cl: same as example 1.

[0060] (2) Au(tht)Cl (0.02 mmol, 10 mg) was dissolved in 3 mL water with 0.06 mmol of the thiol ligand (2-H2mna), 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and stirred for 10 minutes, 2 mg (0.052 mmol) of the reducing agent sodium borohydride was added, stirred at room temperature for 10 hours, then slowly evaporated at room temperature in dark environment to obtain the gold nanoclusters Au 25 (2-Hmna) 15 , the single-step yield was 43%.

[0061] Example 6:

[0062] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically comprising:

[0063] (1) Synthesis of the thiol gold precursor Au(tht)Cl: same as Example 1.

[0064] (2) Au(tht)Cl (0.02 mmol, 10 mg) was dissolved in 3 mL water with 0.06 mmol of the thiol ligand (2-H2mna), 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and stirred for 10 minutes, 2 mg (0.052 mmol) of the reducing agent sodium borohydride was added, stirred at room temperature for 10 hours, then slowly evaporated at room temperature in dark environment to obtain the gold nanoclusters Au 25 (2-Hmna) 15 , the single-step yield was 43%.

[0065] Example 7:

[0066] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically comprising:

[0067] (1) Synthesis of the thiol gold precursor Au(tht)Cl: same as Example 1.

[0068] (2) Au(tht)Cl (0.02 mmol, 10 mg) was dissolved in 3 mL water with 0.06 mmol of the thiol ligand (2-H2mna), 50 μL (0.36 mmol) of triethylamine was added, the solution slowly turned yellow under stirring and stirred for 10 minutes, 2 mg (0.052 mmol) of the reducing agent sodium borohydride was added, stirred at room temperature for 10 hours, then slowly evaporated at room temperature in dark environment to obtain the gold nanoclusters Au 25 (2-Hmna) 15 , the single-step yield was 43%.

[0069] Example 8:

[0070] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, as described in Example 1, except that in step (1), 3-mercaptothiophene is replaced by 2-mercaptothiophene, and other steps and conditions are consistent with Example 1.

[0071] The gold nanocluster Au 25 (2-Hmna) 15 The single-step yield is 25%.

[0072] Example 9:

[0073] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0074] (1) Synthesis of sulfur gold precursor Au(tht)Cl: same as Example 1.

[0075] (2) Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of thiol ligand (6-H2mna) are dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine is added, stirred for 10 minutes (mixed evenly), 1 mg (0.026 mmol) of reducing agent sodium borohydride is added, stirred at room temperature for 10 hours, then slowly evaporate the solvent at room temperature in the dark environment to obtain gold nanocluster Au 25 (6-Hmna) 18 The single-step yield is 21%.

[0076] Example 10:

[0077] A method for preparing a water-soluble gold nanocluster with a crystallographic structure, specifically:

[0078] (1) Synthesis of sulfur gold precursor Au(tht)Cl: same as Example 1.

[0079] (2) Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of thiol ligand (p-mna) are dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine is added, stirred for 10 minutes (mixed evenly), 1 mg (0.026 mmol) of reducing agent sodium borohydride is added, stirred at room temperature for 10 hours, then slowly evaporate the solvent at room temperature in the dark environment to obtain gold nanocluster Au 25 (p-mba) 18 The single-step yield is 36%.

[0080] Comparative Example 1:

[0081] The preparation of gold nanoclusters is as described in Example 1, except that no reducing agent is added during the reaction process in step (2); other steps and conditions are consistent with Example 1.

[0082] i.e. step (2): Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of the thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution turned yellow slowly under stirring and was stirred for 10 minutes, and was stirred at room temperature for 10 hours, and then was slowly evaporated at room temperature in the dark, the product obtained was a mixture of gold nanoclusters with different core numbers, and the gold nanoclusters Au 25 (2-Hmna) 15 .

[0083] Comparative Example 2

[0084] The gold nanoclusters were prepared as described in Example 1, except that in step (2), triethylamine was not added; the other steps and conditions were consistent with Example 1.

[0085] i.e. step (2): Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of the thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution turned yellow slowly under stirring and was stirred for 10 minutes, and was stirred at room temperature for 10 hours, and then was slowly evaporated at room temperature in the dark, the product obtained was a mixture of gold nanoclusters with different core numbers, and the gold nanoclusters Au 25 (2-Hmna) 15 .

[0086] Comparative Example 3

[0087] The gold nanoclusters were prepared as described in Example 1, except that step (1) was not performed, and chloroauric acid was directly mixed with the thiol ligand, and the specific steps were as follows:

[0088] Au(tht)Cl (0.02 mmol, 10 mg) and 0.02 mmol of the thiol ligand (2-H2mna) were dissolved in 3 mL of water, 50 μL (0.36 mmol) of triethylamine was added, the solution turned yellow slowly under stirring and was stirred for 10 minutes, and was stirred at room temperature for 10 hours, and then was slowly evaporated at room temperature in the dark, the product obtained was a mixture of gold nanoclusters with different core numbers, and the gold nanoclusters Au 25 (2-Hmna) 15 .

[0089] Test Example 1: Structural Characterization

[0090] The crystal structure of the gold nanoclusters synthesized above was characterized, and the specific structure is shown in Figures 1-5 .

[0091] (1) The molecular formula of the gold nanocluster prepared in Example 1 is Au 25 (2-Hmna) 15 The crystal structure of which is composed of Au 13 A icosahedral metal core and Au 12 shell Figure 1 , which has an Au-S coordination surface structure different from the classical Au 25 metal core, Au 25 The metal core is protected by 15 2-H2mna ligands. The present application not only discovers a new crystal structure of water-soluble Au 25 nanoclusters that people have long pursued, but also paves the way for exploring the relationship between the structure and performance of water-soluble nanoclusters.

[0092] The molecular formula of the gold nanocluster prepared in Example 9 is Au 25 (6-Hmna) 18 The molecular formula of the gold nanocluster prepared in Example 10 is Au 25 (p-mba) 18 ; The gold nanocluster Au 25 (6-Hmna) 18 , Au 25 (p-mba) 18 The overall structure schematic diagram Figure 2 and Figure 3 indicates that they all have a classical Au 13 icosahedral metal core and Au 12 shell composition, and the overall Au 25 metal core and most of the reported oil-soluble A u25 nanoclusters have the same configuration. Au 25 The metal core is protected by 18 2-H2mna or p-mba ligands.

[0093] In addition, Figure 4 Au 25 (2-Hmna) 15 The most attractive place is that its unique, different from the past Au 25 metal core has not been observed in previously reported Au 25 nanoclusters.

[0094] Figure 5 The mass spectrum of the water-soluble Au 25 gold nanocluster Au 25 (2-Hmna) 15 prepared in Example 1. From this it can be seen that the new water-soluble Au 25 (2-Hmna) 15 gold nanocluster is stable under mass spectrometry conditions.

[0095] Test Example 2: Performance Measurement

[0096] The novel water-soluble Au prepared in Example 1 25 (2-Hmna) 15 Liquid UV spectroscopy was performed on gold nanoclusters, such as... Figure 6 As shown.

[0097] pass Figure 6 It can be seen that Au 25 (2-Hmna) 15 Dissolving in water (1 mg / mL), it exhibits two absorption bands at 390 nm and 510 nm. Figure 7 It can be seen that Au dissolved in water 25 (2-Hmna) 15 (1 mg / mL) remained stable for up to 40 hours. Au was studied. 25 (2-Hmna) 15 Optical properties in aqueous solution (1 mg / mL). For example... Figure 8 As shown, when excited at 400 nm, Au 25 (2-Hmna) 15 It exhibits near-infrared emission in aqueous solution, with an emission peak at 970 nm. This indicates that Au... 25 (2-Hmna) 15 It is a water-soluble gold nanocluster with near-infrared luminescence. The deep penetration of near-infrared luminescence into biological tissues makes it particularly significant in biomedical applications. This invention, Au... 25 (6-Hmna) 18 and Au 25 (p-mba) 18 It does not have near-infrared emission properties.

[0098] pass Figure 9 It can be seen that Au 25 (2-Hmna) 15 It possesses unique near-infrared (NIR) emission and a microsecond lifetime of 8.69 μs in aqueous solution (1 mg / mL) under ambient conditions, which is significant in Au 25 It is rare in the family of nanoclusters.

[0099] In summary, the novel water-soluble Au25 gold nanoclusters synthesized by the present invention not only have atomically precise structures but also exhibit near-infrared luminescence, demonstrating potential applications in biomedicine. Furthermore, the synthesis method disclosed in this invention has the advantages of short synthesis time, simple operation, mild conditions, readily available raw materials, and ease of industrial production.

[0100] The above-described embodiments are merely preferred embodiments of the present application, and are not all the embodiments. Based on the embodiments in the present application, any equivalent replacement, improvement, recombination, etc. obtained without creative labor, all other embodiments, belong to the protection scope of the present application.

Claims

1. A method for preparing water-soluble gold nanoclusters with a crystallographic structure, wherein the gold nanoclusters are Au nanoclusters protected by thiol ligands. 25 Nanoclusters; the thiol ligand is 2-mercaptonicotinic acid (2-H2mna), 6-mercaptonicotinic acid (6-H2mna), or 6-mercaptobenzoic acid ( p -mba); The molecular formula of the gold nanoclusters is Au. 25 (2-Hmna) 15 Au 25 (6-Hmna) 18 Or Au 25 ( p -mba) 18 ; The method for preparing the water-soluble gold nanoclusters with crystallographic structure includes the following steps: (1) Chloroauric acid was dissolved in ethanol, mercaptothiophene was added dropwise, and after stirring the reaction, the mixture was filtered, washed and dried to obtain the thiogold precursor Au(tht)Cl. (2) The gold sulfide precursor Au(tht)Cl, thiol ligand, and triethylamine were fully dispersed in a polar solvent, sodium borohydride was added, and the mixture was stirred to obtain water-soluble gold nanoclusters.

2. The method for preparing water-soluble gold nanoclusters with crystallographic structure according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. Mercaptothiophene is 2-mercaptothiophene or 3-mercaptothiophene; ii. The molar ratio of chloroauric acid to the volume ratio of ethanol is 0.1-0.5 mol / L; iii. The molar ratio of chloroauric acid to mercaptothiophene is (1:0.2) to (1:1); iv. The addition of mercaptothiophene was carried out under stirring conditions; v. The stirring reaction temperature is room temperature, and the stirring reaction time is 1-3 hours.

3. The method for preparing water-soluble gold nanoclusters with crystallographic structure according to claim 1, characterized in that, In step (2), the molar ratio of Au(tht)Cl to thiol ligand is (1:1) to (1:4).

4. The method for preparing water-soluble gold nanoclusters with crystallographic structure according to claim 1, characterized in that, In step (2), the molar ratio of Au(tht)Cl to triethylamine is (1:18) ~ (1:25).

5. The method for preparing water-soluble gold nanoclusters with crystallographic structure according to claim 1, characterized in that, In step (2), the molar ratio of Au(tht)Cl to sodium borohydride is (1:1) to (1:5).

6. The method for preparing water-soluble gold nanoclusters with crystallographic structure according to claim 1, characterized in that, In step (2), the polar solvent is water; the molar ratio of Au(tht)Cl to the volume ratio of the polar solvent is 0.001-0.01 mol / L.

7. The method for preparing water-soluble gold nanoclusters with crystallographic structure according to claim 1, characterized in that, In step (2), the stirring reaction temperature is room temperature and the stirring reaction time is 10-12 h; the reaction solution obtained by the reaction is allowed to slowly evaporate the solvent at room temperature in the dark to obtain water-soluble gold nanoclusters.

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