A gold-copper alloy nanocluster, a preparation method and application thereof

Abstract

The application provides a gold-copper alloy nanocluster and a preparation method and application thereof, and the structure of the gold-copper alloy nanocluster is shown in the following formula: [Au4Cu6(R 1 )2(R 2 )4Cl3](CuCl2); wherein, R 1 is a bis(diphenylphosphine)methane ligand; and R 2 is an adamantane thiol ligand. The preparation method comprises the following steps: taking [Au4Cu4(R 1 )2(R 2 )5] + as a template cluster, occupying the cavity of the template cluster by a copper salt to induce growth nucleation, and then surface size growth occurs. The alloy nanocluster synthesized by the method of the application exhibits aggregation-induced emission (AIE) in a solid state, and the absolute luminescence quantum yield is 18.01%. The application discloses a structure transformation process and mechanism of a CuCl-induced gold-copper alloy nanocluster, and enriches the research on metal ion-induced metal nanocluster size conversion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials and nanomaterial preparation, and particularly relates to a gold-copper alloy nanocluster and a preparation method and application thereof. BACKGROUND

[0002] Metal (such as Cu, Ag, Au, etc.) nanoclusters with atomic precision have unique physical and chemical properties, not only greatly enriching people's understanding of nanomaterials, but also showing broad application prospects in the fields of light emission, catalysis, sensing and biological imaging.

[0003] Bimetallic Au n X m + The second metal atom X of the cluster (X = Cu, Al, Ag, Zn, etc.) plays a special role in the stability and chemical activity of the cluster. Studies have shown that as the number of doped heteroatoms increases, the electronic shell effect exhibited by Au clusters becomes less and less obvious, which will also affect the structural stability of Au clusters. Therefore, people analyze the atomic structure of the cluster to study its structure-property correlation, single crystal x-ray diffraction (SCXRD) analysis, electrospray ionization mass spectrometry (ESI-MS) monitoring and DFT calculation provide a good way to clarify these internal mechanisms. However, understanding the details of regulation at the atomic level is still a great challenge. Based on this, metal ion-induced structure transformation can also be used to regulate the structure, realize the rational development of Au cluster structure functionalization and modification strategy, and adapt to different application requirements.

[0004] Existing literature reports that [Au 25 (PET) 18 ] - Reaction with AgNO3 can bridge two Au 25 (PET) 18 To form Ag2Au 50 (PET) 36 Dimer or form Au 25 Ag2(PET) 18 , and [Au 25 (PET) 18 ] - Reaction with AgSR preferentially forms [Ag x Au 25-x (PET) 18 ] - . [Au 23 (SR) 16 ] - Reaction with active metal precursor Cd(S-c-C6H 11 )2induces conversion to Au 20Cd4(SH)(SR) 19 The metal ion-induced structural transformation process was analyzed by UV-Vis spectroscopy, electrospray ionization (ESI) mass spectrometry and DFT calculation. However, the complexity of the surface structure makes it very difficult to track the details of the transformation, such as where is the active site of the metal ion-induced structural transformation, and what intermediates can be formed in this process. Therefore, a suitable template cluster helps to resolve the details of the active site and intermediates, and helps to understand how the metal ion attacks the starting product, and which intermediates generate the final product as a transition state.

[0005] In addition, the size conversion study of atomically precise metal nanoclusters is the basis for exploring the structure-property correlation of clusters. The present invention aims to trigger the growth of diatomic size by copper salt induction to form another Au-Cu alloy nanocluster, however, through intermediate tracking and theoretical calculation, it is found that the addition of CuSAdm does not cause the reaction, therefore, a new copper salt-induced structural transformation of gold-copper alloy nanoclusters is needed to form a new gold-copper alloy nanocluster. SUMMARY

[0006] To solve the above technical problems, the purpose of the present invention is to provide a gold-copper alloy nanocluster and a preparation method and application thereof. The present invention aims to trigger the growth of [Au4Cu4(R 1 )2(R 2 )5] + to [Au4Cu6(Dppm)2(SAdm)4Cl3] + by copper salt induction, solving the problem that CuSAdm cannot induce the size conversion of Au-Cu clusters.

[0007] To achieve the above-mentioned purposes, the technical solutions of the present invention are as follows.

[0008] A preparation method of a gold-copper alloy nanocluster, comprising the following steps:

[0009] [Au4Cu4(R 1 )2(R 2 )5] + as a template cluster, and the copper salt occupies the cavity of the template cluster to induce growth nucleation, and then surface size growth occurs, to obtain a gold-copper alloy nanocluster;

[0010] The structure of the gold-copper alloy nanocluster is as follows:

[0011] [Au4Cu6(R 1 )2(R 2 )4Cl3](CuCl2);

[0012] Wherein, R 1It is a bis(diphenylphosphine)methane ligand; R 2 It is an adamantane thiol ligand.

[0013] This invention selects Au-Cu alloy nanoclusters [Au4Cu4(Dppm)2(SAdm)5] + The template clusters are based on the following two considerations: 1) There are surface cavities between SAuPs ( Figure 1 1) Where S is SAdm and P is Dppm), this may be a potential location for size growth; 2) Small volume, facilitating mechanism explanation through intermediate tracing and theoretical calculations. Based on experimental observations, from [Au4Cu4(Dppm)2(SAdm)5]... + Initially, the addition of CuSAdm did not trigger a reaction, while CuCl was able to induce the growth of the diatomic size, forming another Au-Cu alloy nanocluster [Au4Cu6(Dppm)2(SAdm)4Cl3]. + Whether using medium-sized copper complexes CuSCy and [Au4Cu4S5] + The cluster reaction still occurs in [Au4Cu4S5]. + Adding HSCy to a control system containing approximately 0.3 equivalents of CuCl can generate medium-sized clusters, namely [Au4Cu5(Dppm)2(SAdm). 6-x (SCy) x ] + .

[0014] We compared [Au4Cu4(Dppm)2(SAdm)5] + →[Au4Cu6(Dppm)2(SAdm)4Cl3] + The mechanism was investigated in detail. Time-dependent electrospray ionization mass spectrometry (ESIMS) tracking and density functional theory (DFT) calculations showed that the spatial volume was the main determinant. The large spatial volume of CuSAdm was unfavorable for access to the cavity, while the previously added CuCl, which had less obstruction, could successfully occupy the cavity to induce nucleation. Once a compact pentagonal double pyramidal nucleus was formed, nucleus growth terminated, and further size growth then involved only surface coverage. This mechanism reveals the structural transformation of CuCl-induced gold-copper alloy nanoclusters and contributes to the understanding of the size transformation of metal nanoclusters induced by metal ions.

[0015] Furthermore, the copper salt is CuCl and / or CuSCy.

[0016] Furthermore, [Au4Cu4(R) 1 )2(R 2 )5] +The molar ratio of copper salt is 1:0.8-1.0.

[0017] Further, the core is a pentagonal bipyramid [Au4Cu5] core. 1 )2(R 2 )5] + [Au4Cu4(R 1 )2(R 2 )5]Br.

[0018] Further, the core is a pentagonal bipyramid [Au4Cu5] core.

[0019] Further, the specific method is as follows:

[0020] [Au4Cu4(R 1 )2(R 2 )5] + The cluster is dissolved in a solvent, then a solid copper salt is added, and a reaction is carried out in the dark, after the reaction is completed, water is added to quench, centrifugation is carried out to obtain an organic solution, the solvent is removed to obtain a crude product, and purification is carried out to obtain [Au4Cu6(R 1 )2(R 2 )4Cl3](CuCl2) alloy nanoclusters.

[0021] Further, the solvent is dichloromethane.

[0022] Further, the specific method for purification is as follows:

[0023] The crude product is washed with n-hexane, then dissolved in dichloromethane, centrifuged, and the supernatant is taken, and a two-phase diffusion method is adopted to crystallize at room temperature by using a dichloromethane / n-hexane mixed solvent with a volume ratio of 1:3 to obtain [Au4Cu6(R 1 )2(R 2 )4Cl3](CuCl2) alloy nanoclusters.

[0024] The application provides application of gold-copper alloy nanoclusters in a fluorescent probe or in preparation of a fluorescent labeling reagent or in preparation of a fluorescent dye reagent or in preparation of a fluorescent anti-counterfeiting identification reagent.

[0025] The application has the following beneficial effects:

[0026] 1. The application aims to study a process that [Au4Cu4(Dppm)2(SAdm)5] + (simplified as [Au4Cu4S5] + ) is induced to grow in size by a copper salt (CuCl) to [Au4Cu6(Dppm)2(SAdm)4Cl3] + (simplified as [Au4Cu6S4Cl3] + ). [Au4Cu4S5]+ The pentagonal bipyramidal core structure with defects has less steric hindrance for CuCl and CuSCy to fill (i.e., to initiate core growth), but not for the bulkier CuSAdm. Once the Au4Cu5 framework is formed, ligand exchange or size growth is prone to occur during the structural transformation. However, due to the compact pentagonal bipyramidal core structure, the latter growth mode only occurs surface capping to form [Au4Cu6(Dppm)2(SAdm)4Cl3] + structure (i.e., core growth stops). The present application shows that the whole transformation process is carried out through five steps of CuCl addition, core tautomerization, Cl - migration, second [CuCl] addition and [CuCl]-[CuSR] exchange. The present application reveals the structural transformation process and mechanism of CuCl-induced gold-copper alloy nanoclusters, enriching the research of metal ion-induced size conversion of metal nanoclusters.

[0027] 2、The method of the present application synthesizes [Au4Cu6(Dppm)2(SAdm)4Cl3] + The alloy nanocluster exhibits aggregation-induced emission (AIE) in the solid state, and the absolute luminescence quantum yield is 18.01%, and the emission lifetime is about 3.30 μs. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the CuCl-induced size conversion reaction mechanism of [Au4Cu4(Dppm)2(SAdm)5] + to [Au4Cu6(Dppm)2(SAdm)4Cl3] + .

[0029] Figure 2 , wherein A) is the optical absorption spectrum of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2).

[0030] , wherein the inset of figure A) is its photoelectron spectrum (eV) graph. B) is the ESI-MS spectrum of [Au4Cu6S4Cl3] + . C) is the x-ray photoelectron spectrum (XPS) graph of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2). D) is the differential pulse voltammetry spectrum of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2).

[0031] Figure 3Crystal structure of [Au4Cu6(Dppm)2(SAdm)4Cl3] (CuCl2).

[0032] Figure 4 Figure A) is [Au4Cu4(Dppm)2(SAdm)5] + Figure B) is [Au4Cu4(Dppm)2(SAdm)5] + Figure B) is [Au4Cu4(Dppm)2(SAdm)5] + ; 2 is [Au4Cu4S4Br] + ; 3 is [Au4Cu5S4Cl2] + ; 4 is [Au4Cu4S5] + ; 5 is [Au4Cu6S4Cl3] + ; 6 is [Au4Cu5S5Cl] + ; 7 is [Au4Cu5S6] + .

[0033] Figure 5 Figure is the energy distribution diagram of DFT calculated size-growth path, relative energy in kcal / mol.

[0034] Figure 6 Figure is the size growth process diagram from [Au4Cu4S5] + to [Au4Cu5S'6] + .

[0035] Figure 7 Figure A) is [Au4Cu6S4Cl3] + emission spectrum of the cluster in solid state or solution state; B) is [Au4Cu6S4Cl3] + emission spectrum of the cluster in 200-290 K solution state under 473 nm excitation; C) is [Au4Cu6S4Cl3] + emission spectrum of the cluster recorded in 100-290 K solid state under 473 nm excitation; D) is [Au4Cu6S4Cl3] + solid state emission lifetime diagram of the cluster at room temperature. DETAILED DESCRIPTION

[0036] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0037] All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without creative labor fall within the scope of the present application.

[0038] In the present application, [Au4Cu4(Dppm)2(SAdm)5] + is abbreviated as [Au4Cu4S5] + .

[0039] [Au4Cu6(Dppm)2(SAdm)4Cl3] + is abbreviated as [Au4Cu6S4Cl3] + .

[0040] [Au4Cu5(Dppm)2(SAdm)5Cl] + is abbreviated as [Au4Cu5S5Cl] + .

[0041] [Au4Cu5(Dppm)2(SAdm)6] + is abbreviated as [Au4Cu5S6] + .

[0042] [Au4Cu4(Dppm)2(SAdm)4Cl1] + is abbreviated as [Au4Cu4S4Cl1] + .

[0043] [Au4Cu4(Dppm)2(SAdm)4Br1] + is abbreviated as [Au4Cu4S4Br1] + .

[0044] [Au4Cu5(Dppm)2(SAdm)4Cl2] + is abbreviated as [Au4Cu5S4Cl2] + .

[0045] [Au4Cu5(Dppm)2(S-c-C6H 11 )6] + is abbreviated as [Au4Cu5S'6] + .

[0046] CuSAdm is copper adamantane thiolate. CuCl is cuprous chloride.

[0047] The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0048] Example 1

[0049] A method of synthesizing a [Au4Cu4(Dppm)2(SAdm)5]Br cluster, comprising the steps of:

[0050] Chloroauric acid (HAuCl4.3H2O, 40 mg, 0.10 mmol) and CuCl2(20 mg, 0.15 mmol) were dissolved in 20 ml of CH3OH (methanol) with 200 mg of TOAB (tetraoctylammonium bromide) under vigorous stirring. After 10 min, bis(diphenylphosphino)methane (Dppm, 50 mg, 13 mmol) and adamantane thiol (AdmSH, 50 mg) were added. The solution changed from yellow-green to light yellow. After 10 min, freshly prepared tert-butylamine borane solution (C4H 14 BN (200 mg, 2.3 mmol) was dissolved in 3 ml of CH3OH). Then, the color slowly changed to purple. This reaction was continued for 10 h at room temperature, and the crude product was obtained by rotary evaporation. The precipitate was washed with excess n-hexane for 3 times to obtain the [Au4Cu4(Dppm)2(SAdm)5]Br cluster.

[0051] Example 2

[0052] A method of synthesizing a [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster, comprising the steps of:

[0053] The [Au4Cu4(Dppm)2(SAdm)5]Br cluster (40 mg) prepared in Example 1 was first dissolved in 10 ml of dichloromethane, and solid CuCl (1.5 mg, 1.0 eq) was added to the dichloromethane solution. After 2 min of further reaction in the dark, the reaction was quenched with water, and the organic solution was obtained by centrifugation, and rotary evaporation to obtain a red precipitate product. The orange-red precipitate was washed with excess n-hexane, dissolved in dichloromethane again, centrifuged, and the supernatant was collected. The red single crystal was obtained by the up-and-down two-phase diffusion method with dichloromethane / n-hexane (1:3) mixed solvent at room temperature for 5-7 days.

[0054] The red single crystal obtained in Example 2 was further determined to be [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) by single crystal x-ray diffraction (SCXRD) and electrospray ionization mass spectrometry (ESI-MS). The specific single crystal data are shown in Table 1.

[0055] Table 1 Crystal data of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster

[0056]

[0057] Example 3

[0058] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was substantially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.9 eq) was added.

[0059] Example 4

[0060] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was substantially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.8 eq) was added.

[0061] Example 5

[0062] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster included the following steps:

[0063] First, the [Au4Cu4(Dppm)2(SAdm)5]Br cluster prepared in Example 1 (40 mg) was dissolved in 10 ml of dichloromethane, and solid CuSCy (0.2 eq) was added to the dichloromethane solution, and reacted in the dark for 2 min, then CuCl (0.6 eq) was added. After another 2 min of dark reaction, it was quenched with water, and the organic solution was obtained by centrifugation, and the red precipitate was obtained by rotary evaporation. The orange-red precipitate was washed with excess n-hexane, dissolved in dichloromethane again, centrifuged, and the supernatant was collected. The two-phase diffusion method was used to crystallize at room temperature for 5-7 days using dichloromethane / n-hexane (1:3) mixed solvent to obtain red single crystals.

[0064] Example 6

[0065] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster included the following steps:

[0066] First, the [Au4Cu4(Dppm)2(SAdm)5]Br cluster prepared in Example 1 (40 mg) was dissolved in 10 ml of dichloromethane, and solid CuSCy (0.2 eq) was added to the dichloromethane solution, and reacted in the dark for 2 min, then CuCl (0.6 eq) was added. After another 2 min of dark reaction, it was quenched with water, and the organic solution was obtained by centrifugation, and the red precipitate was obtained by rotary evaporation. The orange-red precipitate was washed with excess n-hexane, dissolved in dichloromethane again, centrifuged, and the supernatant was collected. The two-phase diffusion method was used to crystallize at room temperature for 5-7 days using dichloromethane / n-hexane (1:3) mixed solvent to obtain red single crystals.

[0067] Comparative Example 1

[0068] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was essentially the same as that of Example 2, except that CuSAdm was used instead of CuCl in Example 2. However, no reaction occurred even after 1 h of reaction in the dark.

[0069] Comparative Example 2

[0070] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was essentially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.7 eq) was added.

[0071] Comparative Example 3

[0072] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was essentially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.6 eq) was added.

[0073] Comparative Example 4

[0074] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was essentially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.5 eq) was added.

[0075] Comparative Example 5

[0076] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was essentially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.4 eq) was added.

[0077] Comparative Example 6

[0078] The synthesis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster was essentially the same as that of Example 2, except that the amount of CuCl added was different, specifically: solid CuCl (0.3 eq) was added.

[0079] Comparative Example 7

[0080] The synthesis method of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster is basically the same as that of Example 2, except that the amount of CuCl added is different, specifically: adding solid CuCl (0.2 eq).

[0081] Comparative Example 8

[0082] The synthesis method of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster is basically the same as that of Example 2, except that the amount of CuCl added is different, specifically: adding solid CuCl (0.1 eq).

[0083] Comparative Example 9

[0084] The synthesis method of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster is basically the same as that of Example 2, except that no solid CuCl is added.

[0085] The reaction mechanism of the above examples is analyzed as follows:

[0086] I. Reaction principle induced by CuCl

[0087] The reaction principle of each of the above examples is shown in Figure 1 . Figure 1 illustrates the size transformation process of [Au4Cu4(Dppm)2(SAdm)5] + to [Au4Cu6(Dppm)2(SAdm)4Cl3] + induced by CuCl, while CuSAdm cannot trigger structural transformation. In order to facilitate the study of intermediates, the HSCy ligand is exchanged with intermediate 1 to generate an intermediate cluster ([Au4Cu5(Dppm)2(SAdm) 6-x (SCy) x ] + ). The specific analysis is as follows:

[0088] Example 2 studies the size transformation process of [Au4Cu4(Dppm)2(SAdm)5] + to [Au4Cu6(Dppm)2(SAdm)4Cl3] + induced by CuCl. However, using CuSAdm of Comparative Example 1 to replace CuCl of Example 2 to react, no reaction occurs after reacting in the dark for 1 h, which indicates that CuSAdm cannot trigger structural transformation.

[0089] Example 5 studies the structural transformation induced by CuSCy, and it is found that CuSCy can only induce [Au4Cu4(Dppm)2(SAdm)5] + to intermediate 2 ([Au4Cu5(Dppm)2(S-c-C6H 11 )6] + , and then still need to use CuCl to induce intermediate 2 to continue to transform into [Au4Cu6(Dppm)2(SAdm)4Cl3] + .

[0090] Example 6 studies the structural transformation induced by CuCl and HSCy, and it is found that after adding 0.3 eq of CuCl, CuCl induces [Au4Cu4(Dppm)2(SAdm)5] + to transform into intermediate 1 ([Au4Cu5(Dppm)2(SAdm)5Cl] + , and after adding HSCy, it can only induce intermediate 1 to transform into intermediate 2, and then still need to use CuCl to induce intermediate 2 to continue to transform into [Au4Cu6(Dppm)2(SAdm)4Cl3] + .

[0091] II. Structural analysis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster

[0092] In order to study the size transformation of [Au4Cu4(Dppm)2(SAdm)5] + induced by CuCl to [Au4Cu6(Dppm)2(SAdm)4Cl3] + , we analyzed the optical absorption spectrum, ESI-MS spectrum, x-ray photoelectron spectrum (XPS) and differential pulse voltammetry spectrum of the [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster prepared in Example 2, and the results are shown in Figure 2 .

[0093] Figure 2 Among them, A) is the optical absorption spectrum of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2). Among them, the inset of figure A) is its photoelectron spectrum (eV) graph. B) is the ESI-MS spectrum of [Au4Cu6S4Cl3] + . C) is the x-ray photoelectron spectrum (XPS) of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2). D) is the differential pulse voltammetry spectrum of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2).

[0094] FromFigure 2 As can be seen from Figure A), the solution of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) dissolved in CH2Cl2 has a distinct peak at 470 nm, and two weak broad peaks at 410 nm and 531 nm, with an energy gap of 2.14 eV.

[0095] Depend on Figure 2 As shown in Figure B), [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) exhibits a weak signal at 2713.41 Da, belonging to [Au4Cu6(Dppm)2(SAdm)4Cl3]. + The peak of the complete molecular ion. The signal at a mass-to-charge ratio of 2614.40 Da belongs to the [Au4Cu6(Dppm)2(SAdm)4Cl3] ion. + [Au4Cu5(Dppm)2(SAdm)4Cl2] obtained by removing CuCl + This indicates that CuCl is easily dissociated under electron spraying.

[0096] Depend on Figure 2 As can be seen from Figure C), [Au4Cu6S4Cl3] + The cluster has 2e free valence electrons (2 = 10⁻⁷⁻¹), similar to [Au₄Cu₄S₅]. + (2 = 8-5-1) Similar. XPS analysis showed an Au / Cu atomic ratio of 3.95 / 6.05, consistent with the single-crystal structure data in Table 1. In [Au4Cu6S4Cl3] + Cu 2p3 / 2 The peak is located at 933.15 eV, indicating that [Au4Cu6S4Cl3] + The valence state of Cu atoms in Cu is close to that of Cu(I).

[0097] [Au4Cu6S4Cl3] + Au 4f7 / 2 The peak appears at a binding energy of 85.02 eV, indicating that [Au4Cu6S4Cl3] + The charge state of Au atoms is close to 1 (i.e., Au(I)).

[0098] according to Figure 2 The [Au4Cu6S4Cl3] shown in Figure D) + The differential pulse voltammetry spectrum shows that [Au4Cu6S4Cl3] + The distance between the first oxidation peak and the first reduction peak (O1-R1) is 2.03V.

[0099] III. Stability of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster

[0100] We also dissolved [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster in dichloromethane and recorded its UV-Vis absorption spectra at room temperature as a function of time to evaluate the stability of the bimetallic alloy cluster prepared in Example 2. The results show that [Au4Cu6S4Cl3] + A clear UV-vis peak was still observed, thus indicating that the [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) bimetallic alloy cluster prepared in Example 2 is stable in CH2Cl2solution at room temperature.

[0101] IV. Crystal structure analysis of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster

[0102] Figure 3 Crystal structure of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster.

[0103] The single crystal structure analysis of Table 1 and Figure 3 indicates that [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) crystallizes in the P2c / 1 space group. The nanocluster contains 4 gold atoms, 6 copper atoms, 2 Dppm ligands, 4 -SAdm ligands, and 3 chloride ions. Also, one [CuCl2] + counterion was found in each [Au4Cu6S4Cl3] - cluster, verifying the charge state of “+1”. In the packing model of [Au4Cu6S4Cl3] + , we observed the interlayer distance and the default view from the b-axis, where the interlayer distance can be the cause of the strong aggregation-induced emission (AIE) phenomenon. The Au-Au bond lengths of (DppmAu2)2complex are 3.154, 2.671, and The Cu-S bond lengths vary in the range of The Cu-Cl bond lengths vary in the range of From the structure of Figure 3 , [Au4Cu6S4Cl3] + can be regarded as two DppmAu2blocks inserted into the Cu6(SAdm)4Cl3structure. Similarly, the structure of [Au4Cu4(SAdm)5(Dppm2)] + precursor can be regarded as two (DppmAu2)2blocks inserted into the Cu4(SAdm)5structure.

[0104] V. Mechanism analysis of the transformation induced by CuCl

[0105] To investigate the mechanism of the transformation of [Au4Cu4S5] + into [Au4Cu6S4Cl3] + , we performed experimental and theoretical calculations, see Figure 4 and Table 2.

[0106] Figure 4 In Figure A), UV-Vis spectra of [Au4Cu4(Dppm)2(SAdm)5] + as a function of the amount of CuCl added; Figure B) is the ESI-MS spectra of the related samples of [Au4Cu4(Dppm)2(SAdm)5] + as a function of the amount of CuCl added. In Figure B), 1 is [Au4Cu4S4Cl] + ; 2 is [Au4Cu4S4Br] + ; 3 is [Au4Cu5S4Cl2] + ; 4 is [Au4Cu4S5] + ; 5 is [Au4Cu6S4Cl3] + ; 6 is [Au4Cu5S5Cl] + ; 7 is [Au4Cu5S6] + .

[0107] Table 2. Different amounts of CuCl added and the changes in the cluster structure

[0108]

[0109] Note: 1 is [Au4Cu4S4Cl] + ; 2 is [Au4Cu4S4Br] + ; 3 is [Au4Cu5S4Cl2] + ; 4 is [Au4Cu4S5] + ; 5 is [Au4Cu6S4Cl3] + ; 6 is [Au4Cu5S5Cl] + ; 7 is [Au4Cu5S6] + . The transformation rate refers to the transformation rate of [Au4Cu4(Dppm)2(SAdm)5] + to [Au4Cu6(Dppm)2(SAdm)4Cl3] + .

[0110] First, [Au4Cu4(Dppm)2(SAdm)5]Br (40 mg) was dissolved in 10 ml CH2Cl2. Then, CuCl (1.5 mg) dissolved in 1 ml CH3CN was added to the CH2Cl2solution in 100 μL aliquots every minute and sampled for detection.

[0111] From Figure 4 Figure A) it can be seen that [Au4Cu4S5] + has two peaks at 525 nm and 595 nm. After each drop, the peaks gradually blue-shifted and a weak peak appeared at 420 nm, accompanied by a change in solution color from purple to orange. Given the fast reaction rate, ESI-MS tracking was performed with the stepwise addition of CuCl (synchronized with UV-Vis tracking) to reduce the reaction rate and identify possible intermediates.

[0112] From Figure 4 Figure B) it can be seen that when 0.1 equivalents of CuCl were added, the formation of [Au4Cu5(Dppm)2(SAdm)5Cl] + from [Au4Cu4S5] + (the complex is abbreviated as [Au4Cu5S5Cl] + ) could be easily observed in the ESI-MS spectrum. With increasing amounts of CuCl, the formation of [Au4Cu5(Dppm)2(SAdm)6] + (the complex is abbreviated as [Au4Cu5S6] + ) and [Au4Cu5(Dppm)2(SAdm)4Cl2] + (the complex is abbreviated as [Au4Cu5S4Cl2] + ) was also observed in the corresponding ESI-MS tracking results.

[0113] When 0.3 equivalents of CuCl were added to the solution, the signals corresponding to [Au4Cu5S5Cl] + and [Au4Cu5S6] + were very obvious in the ESI-MS spectrum, and the UV-Vis spectrum of this component was similar to that of [Au4Cu5(Dppm)2(S-c-C6H 11 )6] + (the complex is abbreviated as [Au4Cu5S'6] + ). At the same time, [Au4Cu5S5Cl] + and [Au4Cu5S6] +The obvious signal peaks prompted us to hope to isolate the relevant intermediates during the size growth process, but the intermediates were easily decomposed during rotary evaporation, producing white turbid substances. This indicates that the reaction intermediates containing [Au4Cu5S5Cl] + and [Au4Cu5S6] + are not very stable. This can be due to the steric hindrance between the large volume -SAdm ligands being too large. Therefore, in this case, we believe that the less sterically hindered HS-c-C6H 11 can be used to stabilize the intermediates. Under the same conditions, i.e. the intermediates (in [Au4Cu4S5] + and the control system with the addition of about 0.3 equivalents of CuCl) and HS-c-C6H 11 ligand exchange reaction, the UV-vis spectrum of the intermediate becomes [Au4Cu5S'6] + . The resulting product is stably extracted and determined by ESI-MS to be [Au4Cu5S' x S 6-x ] + (x = 1-6), which indicates that the size of the thiol can adjust the structure of the cluster.

[0114] When the CuCl content continues to increase (up by 0.3 equivalents), the signals of [Au4Cu5S5Cl] + and [Au4Cu5S6] + begin to slowly decrease, and the signals of [Au4Cu5S4Cl2] + and [Au4Cu6S4Cl3] + begin to increase. In addition, the UV-vis spectrum continues to shift, similar to the UV-vis spectrum of the crystal [Au4Cu6(Dppm)2(SAdm)4Cl3] (CuCl2) dissolved in CH2Cl2. As Figure 2 -B), the complete molecular ion peak of [Au4Cu6(Dppm)2(SAdm)4Cl3] + can only be observed faintly in the ESI-MS spectrum of the crystal dissolved in 0.5 milliliters of dichloromethane and 0.5 milliliters of methanol, while the fragment peak of [Au4Cu5(Dppm)2(SAdm)4Cl2] + is observed due to the removal of one CuCl.

[0115] In combination with Figure 4 the UV-vis spectrum and the change in the signal of the mass spectrum peak, it can be inferred that with the addition of CuCl, the metastable [Au4Cu5S5Cl] + and [Au4Cu5S6] +then slowly converts to the stable [Au4Cu6(Dppm)2(SAdm)4Cl3] + The enrichment starts, leading to [Au4Cu6S4Cl3] + The UV-vis peak of [Au4Cu6S4Cl3]

[0116] [Au4Cu5S4Cl2] + and [Au4Cu6S4Cl3] + become more and more obvious.

[0117] VI. DFT calculation of the energy profile of the size-growth pathway

[0118] Based on the above analysis, we next use DFT to calculate the energy profile of the size-growth pathway, see Figure 5 . Figure 5 The DFT-calculated energy profile of the size-growth pathway. The relative energies are in kcal / mol. As shown in Figure 5 , the whole reaction proceeds through five basic steps: the first addition of [CuCl], core-structure isomerization (i.e. [CuCl] collapse), Cl - migration, the second addition of [CuCl], and [Cl] / [SR] exchange.

[0119] In the first addition of [CuCl] step, five sites are investigated, and site 1 ([Au4Cu5S5Cl1] + ) is the most feasible site. After that, [CuCl] collapses with an energy barrier of 9.3 kcal / mol ([Au4Cu5S5Cl TSS ] + ) to form the intermediate [Au4Cu5S5Cl-2] + . Then the Cl- migration step occurs to generate the more stable intermediate [Au4Cu5S5Cl-4] + . The second addition of [CuCl] ([Au4Cu5S5Cl-4] + → [Au4Cu6S5Cl2] + ) and [Cl] / [SR] exchange ([Au4Cu6S5Cl2] + → [Au4Cu6S4Cl3] + ) are successive exothermic processes. Therefore,

[0120] [Au4Cu6S4Cl3] + is the thermodynamic product of this pathway. The pathway in Figure 5 explains the intermediate [Au4Cu5S5Cl] +It exhibits metastability and is easily formed, while the latter transforms relatively slowly. Figure 2 B and Figure 4 ).

[0121] Meanwhile, DFT calculations show that, through HS-c-C6H 11 Switching engineering, [Au4Cu5S5Cl] + It can be converted to [Au4Cu5S'6] with an exchange energy of -1.4 kcal / mol. + This process demonstrates that an equilibrium exists among these exchanges, potentially enabling the realization of [Au4Cu5S5Cl]. + To [Au4Cu5S'6] + The transformation. For example... Figure 6 As shown.

[0122] Figure 6 For [Au4Cu4S5] + To [Au4Cu5S'6] + The process of size growth.

[0123] Depend on Figure 6 It can be seen that CuSAdm substitution of CuCl leads to a significant increase in the energy barrier of the first step CuSAdm, and the intermediate [Au4Cu5(Dppm)2(SAdm)6] is formed. + With [Au4Cu4S5] + The precursor is isoenergetic. Therefore, it can be understood that replacing -SAdm with -SCy, which has less steric hindrance, is thermodynamically highly feasible. These results are consistent with [Au4Cu5S]. 6-x S' x ] + The structure (measured by ESI-MS) and [Au4Cu5S'6] under similar conditions + Their crystal structures are consistent.

[0124] VII. AIE effect of the [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster

[0125] The [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster prepared in Example 2 of this invention exhibits a strong AIE effect, see Figure 7 . Figure 7 In the given information, A) is [Au4Cu6S4Cl3]. + The emission spectra of the cluster in solid or solution states; B) is [Au4Cu6S4Cl3]. + The emission spectra of the cluster in solution at 200-290 K under 473 nm excitation; C) is [Au4Cu6S4Cl3]. +The emission spectra of the cluster recorded in the solid state at 100-290 K under 473 nm excitation; D) is [Au4Cu6S4Cl3]. + Solid-state emission lifetime of clusters at room temperature.

[0126] Depend on Figure 7 As can be seen from Figure A), compared to the solution state, [Au4Cu6S4Cl3] + Nanoclusters exhibit strong photoluminescence (PL) under solid-state aggregation-induced emission (AIE). Figure 7 As shown in Figure B), under 470 nm excitation, the [Au4Cu6S4Cl3] in the CH2Cl2 solution... + The nanoclusters emitted light at 740 nm; and as the temperature decreased from 290 K to 200 K, the solution [Au4Cu6S4Cl3] showed increased fluorescence. + The luminescence intensity increased by approximately 10 times; the temperature-dependent emission spectrum in Figure B) indicates that temperature changes have a significant impact on fluorescence in solution. Figure 7 As shown in Figure C), when the temperature decreases from 290K to 100K, the solid [Au4Cu6S4Cl3]... + The emission peak of the nanoclusters remained unchanged at 719 nm (λex. = 473 nm), while the PL intensity increased by approximately 2.4 times. Figure 7 As can be seen from Figure D), [Au4Cu6S4Cl3] + The absolute quantum yield (QY) of the nanoclusters in the solid state is 18.01%, and the emission lifetime is approximately 3.30 μs.

[0127] VIII. Conclusion

[0128] In Example 2 of this invention, a small gold-copper alloy nanocluster, [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2), was obtained by triggering a structural transformation of [Au4Cu4(Dppm)2(SAdm)5]Br with CuCl. Furthermore, the structure of [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) was determined using single-crystal X-ray crystallography. Mass spectrometry tracking and joint density functional theory calculations during the structural transformation process revealed that this transformation is manifested through a process of first inducing nucleus growth (forming a compact pentagonal bipyramidal Au4Cu5 core), followed by surface capping. This process includes five main steps: first addition of [CuCl], core structural tautomerism (i.e., [CuCl] collapse), Cl- migration, second addition of [CuCl], and exchange of [Cl] / [SR]. Additionally, [Au4Cu5(Dppm)2(SAdm)6] modified with HSAdm ligands was also observed. + / [Au4Cu5(Dppm)2(SAdm)5Cl]+ Compared with the large steric hindrance that can only be observed and measured in solution, small size ligands such as Cl / HSCy help stabilize the [Au4Cu6(Dppm)2(SAdm)4Cl3] and [Au4Cu5(Dppm)2(SCy)6] nanoclusters. Moreover, the [Au4Cu6(Dppm)2(SAdm)4Cl3](CuCl2) cluster obtained in Example 2 of the present application has a strong AIE effect. The present application discloses the structural transformation process and mechanism of the gold-copper alloy nanocluster induced by CuCl, enriching the research on the size conversion of metal nanoclusters induced by metal ions.

[0129] The above merely provides the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present application shall fall within the scope of the present application.

Claims

1. A method for preparing a gold-copper alloy nanocluster, characterized in that, The method comprises the following steps: With [Au4Cu4(R 1 )2(R 2 )5] + As template clusters, copper salts occupy the cavities of the template clusters to induce growth and nucleation, forming compact pentagonal double pyramidal nuclei, which then undergo surface size growth to obtain gold-copper alloy nanoclusters. The structure of the gold-copper alloy nanocluster is shown in the following formula: [Au4Cu6(R 1 )2(R 2 )4Cl3](CuCl2); wherein R 1 is a bis(diphenylphosphine) methane ligand; R 2 is an adamantane thiol ligand; The copper salt is CuCl and / or CuSCy; [Au4Cu4(R 1 )2(R 2 )5] + The molar ratio to copper salt is 1:0.8-1.

0.

2. The method of claim 1, wherein the gold-copper alloy nanoclusters are prepared by the method comprising: said [Au4Cu4(R 1 )2(R 2 )5] + is [Au4Cu4(R 1 )2(R 2 )5]Br.

3. The method for preparing gold-copper alloy nanoclusters according to claim 1, characterized in that, The core is a pentagonal bipyramid [Au4Cu5] core.

4. The method of claim 1, wherein the gold-copper alloy nanoclusters are prepared by the method comprising: The specific method is as follows: [Au4Cu4(R 1 )2(R 2 )5] + The cluster is dissolved in solvent, then solid copper salt is added, and the reaction is carried out in the dark. After the reaction is completed, water is added to quench, centrifugation is performed to obtain an organic solution, the solvent is removed to obtain a crude product, and purification is performed to obtain [Au4Cu6(R 2 )2(R 1 )4Cl3](CuCl2) alloy nanoclusters.

5. The method for preparing gold-copper alloy nanoclusters according to claim 4, characterized in that, The solvent is dichloromethane.

6. The method of claim 4, wherein the gold-copper alloy nanoclusters are prepared by the method comprising: The specific method of the purification is as follows: The crude product was washed with n-hexane, then dissolved in dichloromethane, centrifuged, and the supernatant was crystallized by the up-and-down two-phase diffusion method at room temperature using a volume ratio of 1:3 of dichloromethane / n-hexane mixed solvent to obtain [Au4Cu6(R 1 )2(R 2 )4Cl3] (CuCl2) alloy nanoclusters.

7. A gold-copper alloy nanocluster prepared by the method in any one of claims 1-6.

8. Use of the gold-copper alloy nanocluster in claim 7 as a fluorescent probe, or in the preparation of a fluorescent labeling reagent, or in the preparation of a fluorescent staining reagent, or in the preparation of a fluorescent anti-counterfeiting identification reagent.

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