A method for preparing metal and alloy nanoclusters

Abstract

The application discloses a preparation method of metal and alloy nanoclusters, which comprises the following steps: S1, weighing a certain amount of N-heterocyclic-2-thione ligand and metal salt, dissolving in a proper amount of solvent, fully stirring, and uniformly mixing to obtain a corresponding metal complex; S2, continuously stirring, observing color change, and continuously reacting for a period of time to obtain a crude product; and S3, slowly evaporating in the dark to obtain a single crystal of the metal and alloy nanoclusters; and the application provides a simple, high-yield and good-crystallinity method for preparing metal and alloy nanoclusters by using N-heterocyclic-2-thione organic ligand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compound synthesis, in particular to a preparation method of metal and alloy nanoclusters. BACKGROUND

[0002] Metal nanoclusters are relatively stable aggregates composed of several to several thousand metal atoms through physical or chemical binding force, and the size thereof is comparable to the Fermi wavelength of electrons, generally less than 3nm. Due to the special structure of metal nanoclusters, the metal nanoclusters usually exhibit the properties of molecules, thereby exhibiting excellent physical and chemical properties such as optics, electricity, magnetism, catalysis, chirality and the like.

[0003] Generally, the synthesis methods of metal nanoclusters mainly include the following four kinds: the first kind is a reduction growth method, and the speed of reaction depends on the difference in reducing ability of a reducing agent, and common ones include a strong reducing agent sodium borohydride, a mild reducing agent sodium cyanoborohydride and CO and the like. The second kind is a seed growth method, which is a method of gradually growing a smaller size metal nanocluster into a larger size metal nanocluster by using the smaller size metal nanocluster as a seed. The third kind is an alloying method, which is a method of gradually exchanging the motifs on the surface of the original nanocluster by using a certain amount of external motifs to realize metal exchange, thereby obtaining alloy nanoclusters doped with different metals. The fourth kind is a ligand exchange method, which is a method of generating nanoclusters protected by another ligand or multiple ligands by exchanging peripheral protective ligands. However, most of the synthesis processes of metal nanoclusters are complex, and the thermodynamic and kinetic processes need to be strictly controlled, and the yield is low. In addition, the use of reducing agents will cause pollution, which does not meet the principle of green chemistry. Therefore, it is urgent to develop new ligands and synthesis methods for efficient synthesis of nanoclusters.

[0004] At present, the ligands used for synthesizing metal nanoclusters mainly include three categories of thiol ligands, alkyne ligands and phosphine ligands, but the yields of nanoclusters synthesized by these ligands are uneven, and the methods are complex. SUMMARY

[0005] In view of the above problems, the present application provides a method for preparing metal and alloy nanoclusters by using N-containing heterocyclic-2-thione organic ligand (new ligand), which is simple, high in yield and good in crystallinity.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] The present application provides a preparation method of metal and alloy nanoclusters, which comprises the following steps:

[0008] S1, a certain amount of N-heterocyclic-2-thione ligand and metal salt are weighed, dissolved in a proper amount of solvent, fully stirred and mixed to obtain a corresponding metal complex;

[0009] S2, continuously stirring, color change is observed, and the reaction is continued for a period of time to obtain the crude product;

[0010] S3, slow evaporation in the dark to obtain single crystals of metal and alloy nanoclusters.

[0011] Preferably, in step S1, an appropriate amount of reducing agent can be added to enhance the reducing property of the N-heterocyclic-2-thione ligand.

[0012] In the present application, whether to add a reducing agent depends on the type of metal salt. For example, in Example 1 and Example 2 of the present application, no reducing agent is needed to prepare silver nanoclusters and copper nanoclusters. However, in Example 3 of the present application, a reducing agent is needed to prepare gold nanoclusters.

[0013] Preferably, step S2 further comprises: filtering the obtained crude product, drying in a vacuum drying oven, repeatedly washing with clean reaction solvent, and then dissolving in an appropriate solvent.

[0014] In the present application, theoretically, the metal salt can be any metal ion-containing salt. However, the present application also screens some metal salts with high nanocluster yield (close to 100%) and good crystallinity, including one or more of HAuCl4·3H2O, Au(SMe2)Cl, Au(tht)Cl, AgNO3, AgBF4, C2AgF3O2, AgPF6, CH3COOAg, Cu(CH3COO)2·H2O, C8H 12 CuF6N4P, CuCl2, CuCl, CuSO4, H2PtCl6·6H2O, K2PtCl6.

[0015] Preferably, in step S1, the N-heterocyclic-2-thione ligand includes chiral and achiral N-containing five-membered heterocyclic rings and N-containing six-membered heterocyclic rings; and more preferably, the structure of the N-heterocyclic-2-thione ligand is as shown in Figure 1 .

[0016] Preferably, in step S1, the molar mass ratio of one kind of metal salt to the N-heterocyclic-2-thione ligand is 1:(1-4).

[0017] Preferably, in step S1, the solvent is one or more of THF, CH3CN, DMA, DMF, DMSO, and CH2Cl2.

[0018] Preferably, in step S2, the reducing agent includes triethylamine.

[0019] Preferably, in step S2, the color change observed refers to the color of the solution changing from colorless to light yellow.

[0020] Preferably, in step S2, the solvent comprises THF, CH2Cl2, DMA, CH3CN, DMF, aniline, DMSO, cyclohexanone.

[0021] In summary, the present application provides a new ligand that can synthesize metal and alloy nanoclusters, N-containing heterocyclic-2-thione ligand, due to its special electronic structure and the existence of thione and thiol two structures in the solubility state, it becomes an excellent ligand for synthesizing clusters. More importantly, the N-containing heterocyclic-2-thione ligand is easy to modify, and by changing the structure of the ligand, the nanoclusters can be endowed with good chiral optical activity and excellent luminescent properties. The present application also proves by experiments that the N-containing heterocyclic-2-thione ligand is used to synthesize metal nanoclusters, the synthesis method is simple (one-pot method), the reaction condition is mild (without heating), the synthesis process is environmentally friendly (without adding reducing agent), the yield is high (close to 100%) and the crystallinity is good.

[0022] Compared with the prior art, the beneficial effects and significant progress of the technical scheme of the present application are that: in the present application, N-containing heterocyclic-2-thione organic ligand is used to synthesize metal and alloy nanoclusters, the ligand structure is easy to modify, the synthesis method is simple (one-pot method), the ligand is widely applicable, the reaction condition is mild (without heating), the synthesis process is environmentally friendly (without adding reducing agent such as sodium borohydride, in line with the principles of green chemistry), the yield is high (close to 100%) and the crystallinity is good. It is suitable for mass production. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical scheme of the present application, the following will briefly introduce the drawings used in the embodiments of the present application.

[0024] Figure 1 is a structure summary of the N-containing heterocyclic-2-thione organic ligand contained in the present application;

[0025] Figure 2 is a reaction mechanism diagram of the metal and alloy nanoclusters prepared by the present application;

[0026] Figure 3 is a single crystal structure of the silver nanoclusters and copper nanoclusters prepared by the present application;

[0027] Figure 4 is a transmission electron microscope (TEM) diagram of the silver nanoclusters and copper nanoclusters prepared by the present application. DETAILED DESCRIPTION

[0028] The application is further described below in connection with specific examples. The examples are only used to illustrate the application and not to limit the scope of the application. Furthermore, it should be understood that after reading the present application, those skilled in the art can make various modifications and changes to the application, and these equivalent forms also fall within the scope of the appended claims.

[0029] In addition, the reaction devices and chemical reagents involved in the following examples and comparative examples are commercially available, and the detection instruments and detection reagents involved are commercially available.

[0030] In the present application, as shown in Figure 2 is a translation mechanism diagram of a preparation method of metal and alloy nanoclusters, comprising the following steps:

[0031] S1, a certain amount of N-heterocyclic-2-thione ligand (the structure of the N-heterocyclic-2-thione organic ligand is as shown in Figure 1 ) and metal salt are weighed, a proper amount of solvent is added for dissolution, and the mixture is fully stirred and uniformly mixed to obtain a corresponding metal complex;

[0032] S2, continue to stir, observe the color change, and continue to react for a period of time to obtain a crude product;

[0033] S3, slowly evaporate in the dark to obtain a single crystal of metal and alloy nanoclusters.

[0034] In a specific embodiment, in step S1, a proper amount of reducing agent can also be added to enhance the reducing property of the N-heterocyclic-2-thione ligand.

[0035] In a specific embodiment, step S2 further comprises: filtering the obtained crude product, drying in a vacuum drying box, repeatedly washing with clean reaction solvent, and then dissolving in a proper solvent.

[0036] In a specific embodiment, in step S1, the metal salt comprises one or more of HAuCl4·3H2O, Au(SMe2)Cl, Au(tht)Cl, AgNO3, AgBF4, C2AgF3O2, AgPF6, CH3COOAg, Cu(CH3COO)2·H2O, C8H 12 CuF6N4P, CuCl2, CuCl, CuSO4, H2PtCl6·6H2O, K2PtCl6.

[0037] In a specific embodiment, in step S1, the N-heterocyclic-2-thione ligand comprises chiral and achiral N-containing five-membered heterocyclic rings and N-containing six-membered heterocyclic rings.

[0038] In one specific embodiment, in step S1, the molar mass ratio of one metal salt to the N-heterocyclic-2-thione ligand is 1: (1-4).

[0039] In one specific embodiment, in step S1, the solvent is one or more of THF, CH3CN, DMA, DMF, DMSO and CH2Cl2.

[0040] In one specific embodiment, in step S2, the reducing agent includes triethylamine.

[0041] In one specific embodiment, in step S2, the color change observed refers to the color of the solution observed from colorless to light yellow.

[0042] In one specific embodiment, in step S2, the solvent includes THF, CH2Cl2, DMA, CH3CN, DMF, aniline, DMSO, cyclohexanone.

[0043] Example 1

[0044] The preparation method of the silver nanoclusters of the present embodiment specifically includes the following steps:

[0045] 1.1, weigh a certain amount of N-heterocyclic-2-thione ligand and metal salt (containing silver ion) into a 5 mL single crystal bottle, add an appropriate amount of solvent to dissolve;

[0046] 1.2, mix well to obtain a clear and transparent solution;

[0047] 1.3, slowly evaporate in the dark (filter the obtained clear solution with a 0.22 μm needle filter, seal with a sealing film, and place it in a dark room at room temperature for 3-15 days) to obtain silver nanocluster crystals (the crystal structure of the silver nanocluster is shown in Figure 3 a).

[0048] The N-heterocyclic-2-thione ligand mainly refers to chiral and achiral five-membered N-heterocycles and six-membered N-heterocycles, and the metal salt mainly refers to one of AgNO3, AgBF4, C2AgF3O2, AgPF6, CH3COOAg; the molar mass ratio of the metal salt to the N-heterocyclic-2-thione ligand is one of 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4; the appropriate amount of solvent refers to a solvent volume of 1-4 mL; the added solvent is two of THF, CH3CN, DMA, DMF, DMSO and CH2Cl2; the volume ratio of the mixed solvent is one of 1:1, 2:1, 3:1; the mixing process can be ultrasonic or stirring.

[0049] Example 2

[0050] The preparation method of the copper nanoclusters of the embodiment specifically comprises the following steps:

[0051] 2.1, a certain amount of N-heterocyclic-2-thione ligand and metal salt (containing copper ion) is weighed in a 25 mL single-neck flask, dissolved with an appropriate amount of solvent, stirred thoroughly, and mixed uniformly to obtain a corresponding metal complex.

[0052] The metal salt used is Cu(CH3COO)2·H2O, C8H 12 one of CuF6N4P, CuCl2, CuCl, and CuSO4. The N-containing heterocyclic 2-thione used covers chiral and achiral five-membered N-heterocycles and six-membered N-heterocycles. The molar mass ratio of the metal salt to the N-heterocyclic-2-thione ligand is one of 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, and 1:4. The appropriate amount of solvent has a volume of 5-15 mL, and the stirring rate is 500-800 r / min. The solvent added is one of THF, CH3CN, DMA, DMF, DMSO, and CH2Cl2, or a mixed solvent of two of them.

[0053] 2.2, the obtained crude product is filtered and dried in a vacuum drying box, repeatedly washed with clean reaction solvent, and then dissolved with an appropriate solvent;

[0054] The repeatedly washing with the reaction liquid means washing until the filtrate becomes colorless. Then, an appropriate solvent is selected for dissolution. The solvents used here mainly include THF, CH2Cl2, DMA, CH3CN, DMF, aniline, DMSO, cyclohexanone, etc.

[0055] 2.3, slow evaporation in the dark (after dissolution, the liquid is filtered with a 0.22 μm needle filter. The seal is sealed with a 10 mL syringe needle, and 1-3 holes are punched. Place at room temperature in the dark for 3-15 days), to obtain a crystal of copper nanoclusters (the crystal structure of the copper nanoclusters is shown in FIG. b). Figure 3 b).

[0056] Example 3

[0057] The preparation method of the gold nanoclusters of the embodiment specifically comprises the following steps:

[0058] 3.1, the N-heterocyclic-2-thione ligand is prepared into a mother liquor with a certain concentration, an appropriate amount of triethylamine is added, stirred thoroughly for a period of time, then a metal salt (containing gold ion) is prepared into a mother liquor with a certain concentration, and the above-mentioned mixed system is added and reacted for a specific time;

[0059] The metal salt used is one of HAuCl4.3H2O, Au(SMe2)Cl, and Au(tht)Cl. The N-heterocyclic-2-thione organic ligand used mainly refers to chiral and non-chiral five-membered N-heterocyclic and six-membered N-heterocyclic. The mother liquor concentration of the N-heterocyclic-2-thione ligand is one of 5, 6, 7, or 8 mg / mL, and the gold salt mother liquor concentration is one of 5, 6, 7, or 8 mg / mL. The volume of triethylamine added is not less than 5-15 μL. The total volume of the reaction solution is 2-5 mL, and the stirring rate is 500-800 r / min. The stirring time after adding triethylamine is 3-10 min. The reaction time after adding the metal salt is 10 min-2 h. The solvent used for preparing the N-heterocyclic-2-thione mother liquor is one of THF, CH2Cl2, DMA, DMF, DMSO, and CH2Cl3, and the solvent used for preparing the metal salt mother liquor is one of CH3CN, MeOH, and EtOH.

[0060] 3.2, Mix well;

[0061] 3.3, After the reaction is completed, centrifugation (the speed of the centrifuge is 8000-12000 r / min), and the supernatant is slowly volatilized in the dark to obtain the crystal of gold nanoclusters.

[0062] Example 4

[0063] The preparation method of the alloy nanoclusters of the embodiment specifically includes the following steps:

[0064] 4.1, A certain amount of N-heterocyclic-2-thione ligand and metal salt (containing two kinds of copper ions and silver ions) are weighed in a 25 mL single-neck flask, dissolved with an appropriate amount of solvent, stirred well, mixed uniformly, and the corresponding metal complex is obtained;

[0065] The metal salt used is one of AgNO3, AgBF4, C2AgF3O2, AgPF6, CH3COOAg, Cu(CH3COO)2.H2O, C8H 12 CuF6N4P, CuCl2, CuCl, and CuSO4. The N-heterocyclic-2-thione used covers chiral and non-chiral five-membered N-heterocyclic and six-membered N-heterocyclic. The molar mass ratio of the metal salt to the N-heterocyclic-2-thione ligand is one of 1:1:2, 1:1:3, 1:1:4, 1:1:5, and 1:1:6. The appropriate amount of solvent is 5-15 mL, and the stirring rate is 500-800 r / min. The solvent added is one of THF, CH3CN, DMA, DMF, DMSO, and CH2Cl2, or a mixed solvent of one or two of them.

[0066] 4.2, The obtained crude product is filtered, dried in a vacuum drying oven, washed repeatedly with clean reaction solvent, and then dissolved in a proper solvent;

[0067] In the process, repeatedly washing with the reaction solution means washing until the filtrate becomes colorless. Then, the obtained product is dissolved in a proper solvent, such as THF, CH2Cl2, DMA, CH3CN, DMF, aniline, DMSO, cyclohexanone, etc.

[0068] 4.3, Slow evaporation in the dark (after dissolution, the liquid is filtered with a 0.22 μm needle filter, sealed with a sealing film, and then 1-3 holes are punched with a needle of a 10 mL syringe, and the product is slowly evaporated in the dark at room temperature for 3-15 days) to obtain the crystal of the alloy nanocluster.

[0069] Example 5

[0070] The silver nanocluster prepared in Example 1 and the copper nanocluster prepared in Example 2 are observed under a transmission electron microscope. The transmission electron microscope (TEM) test method comprises the following steps: grinding the silver nanocluster prepared in Example 1 and the copper nanocluster prepared in Example 2 into powder, then ultrasonically dispersing in ethanol for 10 min, and then dropping 5 μL of the suspension on a copper mesh. The prepared nanocluster is dissolved in ultrapure water to prepare a 0.01 M mother liquor, then diluted 100 times, and then 5 μL of the suspension is dropped on a copper mesh. The product is dried in a vacuum drying oven at 60°C, and then observed under a transmission electron microscope.

[0071] The results are shown in FIG. 1. Figure 4 As can be seen from the figure, the micro-morphology of the synthesized Ag nanocluster and Cu nanocluster is spherical, the nanocluster has good dispersibility and uniform size, and the average particle size is about 2 nm, which verifies the expected results.

[0072] In summary, according to the present application, a metal and alloy nanocluster is prepared by using a N-containing heterocyclic-2-thione as a ligand and corresponding metal salt in a suitable solvent environment. The method is simple (one-pot method), the reaction condition is mild (no heating is needed), the synthesis process is environmentally friendly (no reducing agent such as sodium borohydride is needed, which conforms to the principle of green chemistry), the yield is high (close to 100%), and the crystallinity is good. Through this method, a crystal suitable for X-ray single crystal diffraction can be obtained, and the structure of the nanocluster is accurately known. In addition, the prepared nanocluster has spherical micro-morphology, good dispersibility, uniform size, and an average particle size of about 2 nm, as can be seen from the transmission electron microscope (TEM) image.

[0073] The applicant declares that, during the description process in the above specification:

[0074] The terms "the present embodiments", "the present embodiments", "as shown", "further", "further improved technical solutions" and the like mean that the specific features, structures, materials or characteristics described in the embodiments or examples are included in at least one embodiment or example of the present application; in the specification, the illustrative description of the above terms is not necessarily for the same embodiment or example, and the specific features, structures, materials or characteristics described can be combined or combined in any one or more embodiments or examples in a suitable manner; in addition, the ordinary skilled in the art can combine or combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0075] Finally, it should be noted that:

[0076] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them;

[0077] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and the non-essential improvements and adjustments or replacements made by the skilled in the art according to the content of the specification are all within the scope of the present application.

Claims

1. A method for preparing metal and alloy nanoclusters, characterized in that, The method comprises the following steps: S1, a certain amount of N-heterocyclic-2-thione ligand, reducing agent triethylamine and metal salt are weighed, a proper amount of solvent is added for dissolution, and the mixture is fully stirred and uniformly mixed to obtain a corresponding metal complex; the metal salt comprises one or more of HAuCl4·3H2O, Au(SMe2)Cl and Au(tht)Cl; the N-heterocyclic-2-thione ligand comprises chiral and achiral N-containing five-membered heterocycle and N-containing six-membered heterocycle; the molar mass ratio of one kind of metal salt to the N-heterocyclic-2-thione ligand is 1:(1-4); the mother liquor concentration of the N-heterocyclic-2-thione ligand is one of 5, 6, 7 or 8 mg / mL; and the volume of the added triethylamine is 5-15 μL; S2, continuous stirring is performed, and it is observed that the color of the solution changes from colorless to light yellow; the reaction is continued for a period of time to obtain a crude product; S3, single crystals of metal and alloy nanoclusters are obtained by slow evaporation in the dark.

2. The method for preparing metal and alloy nanoclusters as described in claim 1, characterized in that, Step S2 further comprises: filtering the obtained crude product, drying in a vacuum drying box, repeatedly washing with clean reaction solvent, and then dissolving in a proper solvent.

3. The method for preparing metal and alloy nanoclusters as described in claim 1, characterized in that, In step S1, the metal salt also includes AgN03, AgBF4, C2AgF302, AgPF6, CH3COOAg, Cu(CH3COO)2-H20, C8H 12 CuF6N4P, CuCl2, CuCl, CuS04, H2PtCl6-6H20, K2PtCl6.

4. The method for preparing metal and alloy nanoclusters as described in claim 1, characterized in that, In step S1, the solvent is one or more of THF, CH3CN, DMA, DMF, DMSO and CH2Cl2.

5. The method for preparing metal and alloy nanoclusters as described in claim 1, characterized in that, In step S2, the solvent comprises THF, CH2Cl2, DMA, CH3CN, DMF, aniline, DMSO and cyclohexanone.

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