Chiral silver-palladium nano-cluster as well as preparation method and application thereof

Abstract

The invention belongs to the crossing field of nano materials and coordination chemistry, and particularly relates to a chiral silver-palladium nano-cluster, a preparation method thereof and application of the chiral silver-palladium nano-cluster in aggregation-induced emission and circular polarization emission. The chemical formula of the chiral silver-palladium nano-cluster is C174H180Ag14Cl4P12Pd, the chiral silver-palladium nano-cluster belongs to a monoclinic system, and the chiral silver-palladium nano-cluster has an atomic-scale accurate structure, is small in size (1.82 nm) and good in monodispersity. The chiral nano-cluster shows good chiral optical activity, has an emission peak at 662 nm, has significant chiral optical activity characteristics and circular dichroism signals, also has two characteristics of aggregation-induced emission and circular polarization emission, has an absorption asymmetric factor and an emission asymmetric factor as high as 8.2 * 10 <-4 > and 2.2 * 10 <-3 > respectively, and has important application value.

Description

Technical Field

[0001] The invention belongs to the cross field of nanomaterials and coordination chemistry, and in particular relates to a chiral silver-palladium nanocluster and a preparation method thereof and applications in aggregation-induced luminescence and circularly polarized luminescence. Background Art

[0002] Chiral materials with circularly polarized luminescence (CPL) properties have broad application prospects in three-dimensional holographic display, optical data storage, optoelectronic devices, bioimaging and photonic information processing. In recent years, chiral metal nanoclusters have been regarded as a potential new type of circularly polarized luminescent functional materials due to their excellent optical properties and high tunability of geometric / electronic structures. From the perspective of practical application needs, it is particularly important to develop solid-state CPL materials with high luminescence efficiency. However, when metal nanoclusters are in an aggregated state, the interaction between their excited states often leads to non-radiative energy transitions, resulting in aggregate luminescence quenching (ACQ). In contrast, the concept of aggregation-induced emission (AIE) provides a new strategy for the design of solid-state CPL materials with strong luminescence performance. Specifically, when metal nanoclusters are in an aggregated state, the vibration or rotation within / between clusters is restricted, resulting in enhanced luminescence. Therefore, the preparation of chiral metal nanocluster materials with both AIE properties and CPL characteristics not only broadens the application range of metal nanoclusters, but also plays an important role in many fields.

[0003] Although a variety of strategies have been developed to construct chiral metal nanocluster materials, there are few reports on metal nanoclusters with both AIE and CPL properties and precise structures. This is mainly because combining the three properties of precise structure, aggregation-induced emission properties and circularly polarized emission properties into one material requires multi-dimensional fine control of the structure of the metal cluster. How to construct metal nanoclusters with both AIE and CPL properties and precise structures has become an urgent problem to be solved. Summary of the invention

[0004] In order to solve the above problems in the background technology, one of the objectives of the present invention is to provide a chiral silver palladium nanocluster, which has a precise structure and has both aggregation-induced emission and circularly polarized emission properties.

[0005] To achieve the above object, the present invention adopts the following technical scheme: a chiral silver palladium nanocluster, wherein the chemical formula of the chiral silver palladium nanocluster is C 174 H 180 Ag 14 Cl4P 12 Pd, composed of 14 Ag atoms, 1 Pd atom, 6 chiral R-BDPP / S-BDPP organic ligands and 4 Cl halogen ligands, abbreviated as Ag14 Pd(R / S-BDPP)6Cl4 or R / S-Ag 14 Pd; among them, Ag 14 Pd(S-BDPP)6Cl4 or S-Ag 14 Pd belongs to the monoclinic system and its chiral space group is P21. α=90°, β=109.745(3)°, γ=90°, The molecular weight is 4401.19Da;

[0006] The organic ligand R-BDPP is (2R, 4R)-bis(diphenylphosphino)pentane, and the organic ligand S-BDPP is (2S, 4S)-bis(diphenylphosphino)pentane. The simplified structural formula is as follows:

[0007]

[0008] As a further description of the chiral silver palladium nanocluster structure:

[0009] Preferably, the chiral silver-palladium nanocluster contains an icosahedral cluster core, which is composed of 12 silver atoms and one palladium atom, and the icosahedral cluster core is protected by 6 chiral R-BDPP / S-BDPP organic ligands.

[0010] The second object of the present invention is to provide a method for preparing the chiral silver-palladium nanoclusters described in any one of the above, comprising the following steps:

[0011] S1. Dissolve silver trifluoromethanesulfonate, palladium acetate and chiral phosphine ligand in a mixed solvent of dichloromethane and methanol, add sodium borohydride aqueous solution, react for 10-16 hours at room temperature in the dark, then remove water-soluble impurities in the solution by adding distilled water, and precipitate a crude product with diethyl ether;

[0012] S2. Dissolve the crude product in dichloromethane, introduce ether into the solution for gas phase diffusion to induce crystal formation, collect and air-dry the crystalline product, and obtain chiral silver palladium nanoclusters.

[0013] As a further improvement of the preparation method of chiral silver palladium nanoclusters:

[0014] Preferably, in step S1, dichloromethane and methanol are mixed in a volume ratio of (5-6):1 to form a mixed solvent.

[0015] Preferably, in step S1, the chiral phosphine ligand is (2R, 4R)-2,4-bis(diphenylphosphino)pentane or (2S, 4S)-2,4-bis(diphenylphosphino)pentane.

[0016] Preferably, in step S1, the molar mass ratio of the silver trifluoromethanesulfonate, palladium acetate, chiral phosphine ligand and sodium borohydride contained in the sodium borohydride aqueous solution is 1:(0.1-0.4):(1-1.6):(1-2).

[0017] Preferably, in step S1, the concentration of silver trifluoromethanesulfonate dissolved in a mixed solvent of dichloromethane and methanol is 0.008-0.01 mmol / ml.

[0018] The third object of the present invention is to provide the application of the chiral silver palladium nanoclusters described in any one of the above items in aggregation-induced luminescence and circularly polarized luminescence.

[0019] Further improvement of the application of chiral silver palladium nanoclusters in aggregation-induced emission and circularly polarized emission:

[0020] Preferably, the application process of aggregation-induced luminescence is as follows: 1 mg of chiral silver palladium nanoclusters is dispersed in N,N-dimethylformamide (DMF), and 1 mg of chiral silver palladium nanoclusters is dispersed in a mixed solvent of water with a water volume fraction of 95% and N,N-dimethylformamide (DMF), both of which are configured into a solution with a concentration of 200 ug / mL, and a fluorescence spectrometer is used to measure the emission peak intensity changes of the two solutions, and a transmission electron microscope and a laser particle size analyzer are used to determine the size distribution of the nanoclusters in the two solutions.

[0021] Preferably, the application process of circularly polarized luminescence is as follows: 1 mg of chiral silver palladium nanoclusters is dissolved in dichloromethane to prepare a solution with a concentration of 0.2 mg / mL, and tested using a circular dichroism spectrometer; at the same time, 1 mg of chiral silver palladium nanoclusters is dissolved in dichloromethane to prepare a solution with a concentration of 1.0 mg / mL, and tested using a circular polarization fluorescence spectrometer.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The present invention provides a chiral silver palladium nanocluster, the chemical formula of which is C 174 H 180 Ag 14 Cl4P 12 Pd, the chiral silver palladium nanocluster has an atomic-level precise structure, a small size (~1.82nm), and good monodispersity. The chiral nanocluster exhibits good chiral optical activity, with an emission peak at 662nm, significant chiral optical activity characteristics and circular dichroism signals, and also has two major characteristics of aggregation-induced luminescence and circularly polarized luminescence. The absorption asymmetry factor and emission asymmetry factor are as high as 8.2×10 -4 and 2.2×10 -3 .

[0024] 2) The present invention provides a method for preparing silver-palladium nanoclusters. The synthesis method is simple, the reaction conditions are mild, the cost is low, and no calcination is required. Only easily available raw materials, such as silver salt, (2R, 4R)-2,4-bis(diphenylphosphino)pentane or (2S, 4S)-2,4-bis(diphenylphosphino)pentane, palladium salt and sodium borohydride, are required. Chiral silver-palladium nanoclusters can be prepared simply and quickly by a one-pot method at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of the chiral silver-palladium nanoclusters prepared in Example 1-2 of the present invention;

[0026] Figure 2 is the ultraviolet absorption spectrum of the chiral silver palladium nanocluster solution prepared in Example 1-4;

[0027] Figure 3 is the electrospray high-resolution mass spectrum of the chiral silver palladium nanoclusters prepared in Example 1-4;

[0028] Figure 4 is a particle size distribution diagram of the chiral silver palladium nanoclusters prepared in Examples 1-4;

[0029] Figure 5 The excitation spectrum and emission spectrum of the chiral silver palladium nanoclusters prepared in Examples 1-4;

[0030] Figure 6 The emission spectra of the chiral silver palladium nanoclusters prepared in Examples 1-4 dispersed in equal amounts in mixed solvents of water and DMF in different proportions, wherein the volume fractions of water are f=0 and 95%, respectively;

[0031] Figure 7 This is a particle size distribution diagram of the chiral silver palladium nanoclusters prepared in Example 1-4 dispersed in a water / DMF mixed solvent with a pure water volume fraction of 95%;

[0032] Figure 8 Circular dichroism (CD) spectrum of the chiral silver palladium nanocluster solution prepared in Example 1-4.

[0033] Fig. 9 Graph showing the absorption asymmetry factor of the chiral silver palladium nanocluster solution prepared in Examples 1-4.

[0034] Fig.10 Circularly polarized luminescence spectrum (CPL) of the chiral silver palladium nanocluster solution prepared in Example 1-4.

[0035] Fig.11 Graph showing the emission asymmetry factor of the chiral silver palladium nanocluster solution prepared in Examples 1-4. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing chiral silver palladium nanoclusters, comprising the following steps:

[0039] S1. Silver trifluoromethanesulfonate (15 mg, 0.058 mmol), palladium acetate (3 mg, 0.013 mmol) and (2S,4S)-2,4-bis(diphenylphosphino)pentane (30 mg, 0.068 mmol) were dissolved in a mixed solvent of 6 mL of dichloromethane and 1 mL of methanol, 1 mL of sodium borohydride solution (3 mg / mL, containing 0.079 mmol of sodium borohydride) was added, and the mixture was reacted for 16 h under light-proof conditions, and then water-soluble impurities in the solution were removed by adding distilled water, and a crude product was precipitated with diethyl ether;

[0040] The molar mass ratio of silver trifluoromethanesulfonate, palladium acetate, chiral phosphine ligand and sodium borohydride contained in the sodium borohydride aqueous solution is 1:0.22:1.17:1.36;

[0041] S2. The crude product is dissolved in dichloromethane, diethyl ether is introduced into the solution for gas phase diffusion to induce crystal formation, and the crystalline product is collected and dried to obtain chiral silver palladium nanoclusters.

[0042] Example 2

[0043] This embodiment provides a method for preparing chiral silver palladium nanoclusters, comprising the following steps:

[0044] S1. Silver trifluoromethanesulfonate (15 mg, 0.058 mmol), palladium acetate (4 mg, 0.018 mmol) and (2S,4S)-2,4-bis(diphenylphosphino)pentane (40 mg, 0.091 mmol) were dissolved in a mixed solvent of 6 mL of dichloromethane and 1 mL of methanol, 1 mL of sodium borohydride solution (4 mg / mL, containing 0.106 mmol of sodium borohydride) was added, and the mixture was reacted for 12 h under light-proof conditions, and then water-soluble impurities in the solution were removed by adding distilled water, and a crude product was precipitated with diethyl ether;

[0045] The molar mass ratio of silver trifluoromethanesulfonate, palladium acetate, chiral phosphine ligand and sodium borohydride contained in the sodium borohydride aqueous solution is 1:0.31:1.57:1.83;

[0046] S2. The crude product is dissolved in dichloromethane, diethyl ether is introduced into the solution for gas phase diffusion to induce crystal formation, and the crystalline product is collected and dried to obtain chiral silver palladium nanoclusters.

[0047] Example 3

[0048] This embodiment provides a method for preparing chiral silver palladium nanoclusters, comprising the following steps:

[0049] S1. Silver trifluoromethanesulfonate (15 mg, 0.058 mmol), palladium acetate (1.3 mg, 0.0058 mmol) and (2R, 4R)-2,4-bis(diphenylphosphino)pentane (25.5 mg, 0.058 mmol) were dissolved in a mixed solvent of 5 mL of dichloromethane and 1 mL of methanol, 1 mL of sodium borohydride solution (2.2 mg / mL, containing 0.058 mmol of sodium borohydride) was added, and the mixture was reacted for 14 h under light-proof conditions, and then water-soluble impurities in the solution were removed by adding distilled water, and a crude product was precipitated with ether;

[0050] The molar mass ratio of silver trifluoromethanesulfonate, palladium acetate, chiral phosphine ligand and sodium borohydride contained in the sodium borohydride aqueous solution is 1:0.1:1:1;

[0051] S2. The crude product is dissolved in dichloromethane, diethyl ether is introduced into the solution for gas phase diffusion to induce crystal formation, and the crystalline product is collected and dried to obtain chiral silver palladium nanoclusters.

[0052] Example 4

[0053] This embodiment provides a method for preparing chiral silver palladium nanoclusters, comprising the following steps:

[0054] S1. Silver trifluoromethanesulfonate (15 mg, 0.058 mmol), palladium acetate (5.2 mg, 0.023 mmol) and (2R, 4R)-2,4-bis(diphenylphosphino)pentane (40 mg, 0.091 mmol) were dissolved in a mixed solvent of 5 mL of dichloromethane and 1 mL of methanol, 1 mL of sodium borohydride solution (4.3 mg / mL, containing 0.114 mmol of sodium borohydride) was added, and the mixture was reacted for 11 h under light-proof conditions, and then water-soluble impurities in the solution were removed by adding distilled water, and a crude product was precipitated with diethyl ether;

[0055] The molar mass ratio of silver trifluoromethanesulfonate, palladium acetate, chiral phosphine ligand and sodium borohydride contained in the sodium borohydride aqueous solution is 1:0.4:1.57:1.97;

[0056] S2. The crude product is dissolved in dichloromethane, diethyl ether is introduced into the solution for gas phase diffusion to induce crystal formation, and the crystalline product is collected and dried to obtain chiral silver palladium nanoclusters.

[0057] The chiral silver-palladium nanoclusters of the present invention prepared in Examples 1-4 were further characterized as follows:

[0058] (1) Crystal structure determination

[0059] Under nitrogen protection and low temperature conditions of 193K, the crystal products in Example 1-2 were selected under a microscope and tested using a single crystal X-ray diffractometer (model: Bruker D8 Venture). The Cu-Kα rays were used for diffraction, and the diffraction data were collected by ω scanning. The single crystal structure was solved by the direct method using the SHELXL-97 software program, and the refinement method used the least squares method F2, and the empirical absorption correction used the SADABS program. First, the positions of all non-hydrogen atoms were determined and anisotropic corrections were made. All Ag, Pd, P, Cl and C atoms were directly discovered, and the hydrogen atom positions in the molecule were refined using isotropic calculations. Detailed crystal measurement data are shown in Table 1. Figure 1 As shown, the results show that the molecular formula of the chiral silver palladium nanocluster in Example 1-2 after analysis is C 174 H 180 Ag 14 Cl4P 12 Pd, abbreviated as Ag 14 Pd(S-BDPP)6Cl4 or S-Ag 14 Pd; its precise structure contains an icosahedral cluster core composed of 12 silver atoms and one palladium atom, and the cluster core is protected by 6 S-BDPP chiral ligands.

[0060] The single crystal X-ray diffractometer measured the crystal prepared in Example 3-4, namely Ag 14 Pd(R-BDPP)6Cl4 or R-Ag 14 Pd chiral nanoclusters, the unit cell parameters are α=90°, β=109.70°, γ=90°, R-Ag 14 Pd and S-Ag 14 Pd unit cell parameters (Table 1), UV-visible absorption spectrum ( Figure 2 ) and electrospray ionization high-resolution mass spectrometry ( Figure 3 ) were compared to determine that the S-Ag prepared in Example 1-2 14 The Pd nanoclusters have the same structure and are chiral enantiomers of each other. Specifically, Figure 2 The chiral silver palladium nanoclusters prepared in the above examples 1-4 were dissolved in dichloromethane respectively, and tested by UV8000 (METASH) ultraviolet-visible absorption spectrometer. 14Pd and S-Ag 14 The positions of the ultraviolet absorption peaks of Pd are consistent, indicating that the two have the same structure.

[0061] Figure 3 The chiral nanoclusters prepared in Examples 1-2 and 3-4 were dissolved in methanol and subjected to electrospray ionization high-resolution mass spectrometry (model Xevo G3 QTOF) in positive ion mode. 14 The mass spectrum peak of Pd is at m / z 2201.75Da, corresponding to [Ag 14 Pd(S-BDPP)6Cl4] 2+ ; R-Ag prepared in Example 3-4 14 The mass spectrum peak of Pd is at m / z 2201.76Da, corresponding to [Ag 14 Pd(R-BDPP)6Cl4] 2+ ; S-Ag 14 Pd and R-Ag 14 The mass spectrum peak position and molecular weight of Pd are consistent, further proving that the two are chiral enantiomers of each other.

[0062] Table 1 Main crystallographic parameters

[0063]

[0064]

[0065] R1=∑||Fo|-|Fc|| / ∑|Fo|.wR2=[∑w(F o 2 -F c 2 ) 2 / ∑w(F o 2 ) 2 ] 1 / 2

[0066] (2) Application of the chiral silver palladium nanoclusters of the present invention in aggregation-induced luminescence and circularly polarized luminescence

[0067] The circularly polarized luminescence application includes the following process: dissolving 1 mg of chiral silver palladium nanoclusters in dichloromethane to prepare a solution with a concentration of 0.2 mg / mL, and testing it with a circular dichroism spectrometer; at the same time, dissolving 1 mg of chiral silver palladium nanoclusters in dichloromethane to prepare a solution with a concentration of 1.0 mg / mL, and testing it with a circular polarization fluorescence spectrometer.

[0068] The application of aggregation-induced emission includes the following process: 1 mg of chiral silver palladium nanoclusters are dispersed in N, N-dimethylformamide DMF, and 1 mg of chiral silver palladium nanoclusters are dispersed in a mixed solvent of water / N, N-dimethylformamide DMF with a water volume fraction of 95%, both of which are configured into a solution with a concentration of 200ug / mL, and the volume fraction of water is f=0% and 95%, respectively. The emission peak intensity of the two solutions is measured by a fluorescence spectrometer, and the size distribution of particles in the solution is measured by a transmission electron microscope and a laser particle size analyzer.

[0069] Figure 4 The chiral silver palladium nanoclusters prepared in the above Examples 1-4 were dissolved in DMF, then dropped onto a copper mesh and dried, and then tested using a transmission electron microscope (TEM) (Hitachi HT7700). The results showed that the chiral silver palladium nanoclusters were small and uniform in size, with an average size of 1.82 nm.

[0070] Figure 5 The chiral silver palladium nanoclusters prepared in the above examples 1-4 were dissolved in DMF and tested using a fluorescence spectrophotometer model FL8500 (PerkinElmer). The results showed that Ag 14 The maximum excitation wavelength of Pd(R / S-BDPP)6Cl4 nanocluster is 406nm, and the maximum emission wavelength is 662nm, which belongs to the red light region.

[0071] Figure 6 The chiral silver palladium nanoclusters prepared in the above-mentioned Examples 1-4 are equally dispersed in a water / DMF mixed solvent with a pure water volume fraction of 95% and in a single DMF solvent, and the solution concentration is 200ug / mL. The emission peak intensity of the two solutions is measured by a fluorescence spectrophotometer using a light source with a wavelength of 430nm for excitation. The results show that the emission peak intensity of the chiral silver palladium nanoclusters in a water / DMF mixed solvent with a pure water volume fraction of 95% is 4.5 times that of the single DMF solvent. Under irradiation with a 365nm ultraviolet lamp, the luminescence intensity of the two solutions is significantly contrasted. The above results all indicate that the chiral silver palladium nanoclusters have aggregation-induced emission properties.

[0072] Figure 7 The chiral silver palladium nanoclusters prepared in the above-mentioned Examples 1-4 were dispersed in a water / DMF mixed solvent with a pure water volume fraction of 95%, and the size distribution of the particles in the solution was measured by dynamic light scattering using a Malvern laser particle size analyzer (model: Nano ZS90). The results showed that the average size of the chiral silver palladium nanoclusters was 852 nm, which indicates that the chiral silver palladium nanoclusters have undergone an aggregation process in the water / DMF mixed solvent with a pure water volume fraction of 95%, so the chiral silver palladium nanoclusters have an average particle size of 1.82 nm ( Figure 4 ) increases to 852nm. Figure 6It can be further confirmed that the luminescence enhancement phenomenon of chiral silver palladium nanoclusters in a water / DMF mixed solvent with a pure water volume fraction of 95% is mainly attributed to the aggregation behavior of chiral silver palladium nanoclusters. Specifically, the aggregation effect inhibits the movement between chiral silver palladium nanoclusters, thereby reducing non-radiative transitions and enhancing the luminescence performance of chiral silver palladium nanoclusters.

[0073] Figure 8 The chiral silver palladium nanoclusters prepared in the above Examples 1-4 were dissolved in dichloromethane to prepare a solution with a concentration of 0.2 mg / mL, and tested using a circular dichroism spectrometer (model: JASCO J-1500). The results showed that the chiral silver palladium nanoclusters had significant chiral optical activity, which was characterized by a mirror-symmetric circular dichroism signal.

[0074] Fig. 9 The chiral silver palladium nanoclusters prepared in the above examples 1-4 were dissolved in dichloromethane to prepare a solution with a concentration of 0.2 mg / mL, and tested using a circular dichroism spectrometer (model JASCO J-1500). The results showed that the chiral silver palladium nanoclusters had a large absorption asymmetry factor g at 320 nm. abs , is 8.2×10 -4 .

[0075] Fig.10 The chiral silver palladium nanoclusters prepared in the above Examples 1-4 were dissolved in dichloromethane to prepare a solution with a concentration of 1.0 mg / mL, and tested using a circular polarization fluorescence spectrometer (model: JASCO CPL-300). The results showed that the chiral silver palladium nanoclusters had obvious mirror-symmetric circularly polarized luminescence signals.

[0076] Fig.11 The chiral silver palladium nanoclusters prepared in the above Example 1-2 were dissolved in dichloromethane to prepare a solution with a concentration of 1.0 mg / mL, and tested using a circular polarization fluorescence spectrometer (model JASCO CPL-300). The results showed that the chiral silver palladium nanoclusters had a large circular polarization luminescence asymmetry factor g at 662 nm. lum , is 2.2×10 -3 .

[0077] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A chiral silver-palladium nanocluster, characterized in that: The chemical formula of the chiral silver palladium nanocluster is C 174 H 180 Ag 14 Cl4P 12 Pd, composed of 14 Ag atoms, 1 Pd atom, 6 chiral R-BDPP / S-BDPP organic ligands and 4 Cl halogen ligands, abbreviated as Ag 14 Pd(R / S-BDPP)6Cl4 or R / S-Ag 14 Pd; Among them, Ag 14 Pd(S-BDPP)6Cl4 or S-Ag 14 Pd belongs to the monoclinic system and its chiral space group is P21. α=90°, β=109.745(3)°, γ=90°, The molecular weight is 4401.19Da; The organic ligand R-BDPP is (2R, 4R)-bis(diphenylphosphino)pentane, and the organic ligand S-BDPP is (2S, 4S)-bis(diphenylphosphino)pentane. The simplified structural formula is as follows:

2. The chiral silver palladium nanocluster according to claim 1, characterized in that: The chiral silver-palladium nanocluster contains an icosahedral cluster core, which is composed of 12 silver atoms and one palladium atom. The icosahedral cluster core is protected by 6 chiral R-BDPP / S-BDPP organic ligands.

3. A method for preparing the chiral silver-palladium nanoclusters according to claim 1 or 2, characterized in that: The steps include: S1. Dissolve silver trifluoromethanesulfonate, palladium acetate and chiral phosphine ligand in a mixed solvent of dichloromethane and methanol, add sodium borohydride aqueous solution, react for 10-16 hours at room temperature in the dark, then remove water-soluble impurities in the solution by adding distilled water, and precipitate a crude product with diethyl ether; S2. Dissolve the crude product in dichloromethane, introduce ether into the solution for gas phase diffusion to induce crystal formation, collect and air-dry the crystalline product, and obtain chiral silver palladium nanoclusters.

4. The method for preparing chiral silver palladium nanoclusters according to claim 3, characterized in that: In step S1, dichloromethane and methanol are mixed in a volume ratio of (5-6):1 to form a mixed solvent.

5. The method for preparing chiral silver palladium nanoclusters according to claim 3, characterized in that: In step S1, the chiral phosphine ligand is (2R, 4R)-2,4-bis(diphenylphosphino)pentane or (2S, 4S)-2,4-bis(diphenylphosphino)pentane.

6. The method for preparing chiral silver palladium nanoclusters according to claim 3, characterized in that: In step S1, the molar mass ratio of the silver trifluoromethanesulfonate, palladium acetate, chiral phosphine ligand and sodium borohydride contained in the sodium borohydride aqueous solution is 1:(0.1-0.4):(1-1.6):(1-2).

7. The method for preparing chiral silver palladium nanoclusters according to claim 3, characterized in that: In step S1, the concentration of silver trifluoromethanesulfonate dissolved in a mixed solvent of dichloromethane and methanol is 0.008-0.01 mmol / ml.

8. Use of the chiral silver palladium nanoclusters according to claim 1 or 2 in aggregation-induced luminescence and circularly polarized luminescence.

9. The use of chiral silver palladium nanoclusters in aggregation-induced emission and circularly polarized emission according to claim 8, characterized in that: The application process of aggregation-induced emission is as follows: 1 mg of chiral silver palladium nanoclusters is dispersed in N,N-dimethylformamide (DMF), and 1 mg of chiral silver palladium nanoclusters is dispersed in a mixed solvent of water with a water volume fraction of 95% and N,N-dimethylformamide (DMF). Both are prepared into a solution with a concentration of 200 ug / mL. The emission peak intensity changes of the two solutions are measured by a fluorescence spectrometer, and the size distribution of the nanoclusters in the two solutions is determined by a transmission electron microscope and a laser particle size analyzer.

10. The use of chiral silver palladium nanoclusters in aggregation-induced emission and circularly polarized emission according to claim 8, characterized in that: The application process of circularly polarized luminescence is as follows: 1 mg of chiral silver palladium nanoclusters is dissolved in dichloromethane to prepare a solution with a concentration of 0.2 mg / mL, and tested using a circular dichroism spectrometer; at the same time, 1 mg of chiral silver palladium nanoclusters is dissolved in dichloromethane to prepare a solution with a concentration of 1.0 mg / mL, and tested using a circular polarization fluorescence spectrometer.

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