CN112110955A - AuCu with high phosphorescence quantum yield in air atmosphere14Nanocluster and method for preparing same - Google Patents

Abstract

The invention discloses an AuCu ₁₄ nano-cluster with high phosphorescence quantum yield in air atmosphere and a preparation method thereof, wherein the AuCu ₁₄ nano-cluster is an AuCu alloy nano-cluster protected by mixed ligands and contains 1 Au atom , 14 Cu atoms, 12 4-tert-butyl thiophenol ligands and 6 bis(2-cyanoethyl) phenylphosphine ligands, the periphery is also equipped with a SbF ₆ ^- counter ion; the described The precise structure of the AuCu ₁₄ nanoclusters contains a core of Au atoms and a metal cage composed of 8 Cu(I) atoms. The cluster has high phosphorescence performance at room temperature and air atmosphere, and its relative quantum yield is 71.35%. In the future, the clusters are expected to be designed for practical applications such as LEDs, high-resolution fluorescent nanoprobes, and anti-counterfeiting.

Description

A kind of AuCu14 nanoclusters with high phosphorescence quantum yield in air atmosphere and its preparation method

technical field

The invention belongs to the subject of nanomaterials, in particular to an AuCu ₁₄ nano-cluster with high phosphorescence quantum yield in air atmosphere and a preparation method thereof.

Background technique

In recent years, metal nanoclusters protected by thiol-containing ligands have attracted the attention of scientific researchers due to their unique physicochemical properties. Among them, photoluminescence is one of its important characteristics. The research results show that the photoluminescence of metal nanoclusters has the following characteristics: good optical stability, good biocompatibility, low toxicity, large Stokes shift, and near-infrared luminescence. These characteristics make fluorescent metal nanoclusters have good application prospects in bioimaging, bioprobes, optical devices and other fields. Therefore, the preparation of metal nanoclusters with photoluminescence has become one of the hotspots currently pursued by cluster material scientists.

So far, dozens of clusters with photoluminescence have been discovered. Based on its precise structure, combined with theoretical calculations, the photoluminescence mechanism was studied in detail, and a concentrated and effective method to improve the luminous efficiency was proposed. For example, changing the electron-donating ability of surface ligands, incorporating second metals, utilizing crystallization induction, and maximizing intramolecular motion through "aggregation sedimentation". The application of these methods has improved the luminous efficiency of metal nanoclusters to a certain extent. For example, Lee et al. used the addition of excess TOA ⁺ to transfer Au ₂₂ (GS) ₁₈ from the aqueous phase to the toluene phase, and the luminous efficiency increased to 60 %, however, Au ₂₂ (GS) ₁₈ @TOA is a mixture, which limits its application to some extent. In addition, Wang et al. succeeded in increasing the rod-like luminous efficiency from 0.2% to 40% by utilizing Ag atom doping. Nevertheless, the photoluminescence efficiency of metal nanoclusters with free valence electrons is still generally low (less than 20%). In addition, most of the previously reported emission lifetimes of luminescent metal nanoclusters are usually in the nanosecond range, metal nanoclusters with phosphorescence properties are still relatively rare, and the phosphorescence quantum yield of metal nanoclusters at room temperature still needs to be further improved. This will facilitate metal nanoclusters to become LED light-emitting materials.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the above-mentioned prior art, the present invention provides an AuCu ₁₄ nano-cluster with high phosphorescence quantum yield (71.3%) in air atmosphere and a preparation method thereof. The AuCu ₁₄ nano-cluster of the present invention exhibits good photoluminescence performance, and its precise structure is obtained.

The AuCu ₁₄ nano-cluster of the present invention is an AuCu alloy nano-cluster protected by mixed ligands, comprising 1 Au atom, 14 Cu atoms, 12 4-tert-butylthiophenol ligands and 6 bis( 2 ^- Cyanoethyl) phenylphosphine ligand with a SbF ₆ -counterion at the periphery; the precise structure of the AuCu nanocluster contains an Au atom core and 14 Cu(I) atoms. metal cage.

The AuCu nano-cluster of the present invention has the following molecular formula:

α＝83.358(7)°，β＝62.415(6)°，γ＝65.215(6)°，

[AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₆ ](SbF ₆ ), abbreviated as AuCu ₁₄ , belongs to the triclinic crystal system, and the space group is P-1,

α=83.358(7)°, β=62.415(6)°, γ=65.215(6)°,

The preparation method of the AuCu nano-cluster of the present invention comprises the following steps:

First, 400 μL of sodium tetrabromoaurate aqueous solution (0.1 g/mL), 130 mg of tetraoctylammonium bromide and 15 mL of dichloromethane were added to a 100 mL pear-shaped flask, and after 30 minutes, 150 μL of 4-tert-butylthiophenol was added into the reaction system; after 60 minutes of reaction, 80 mg of Cu(NO ₃ ) ₂ was dissolved in 5 mL of methanol and added to the reaction system; after 30 minutes of reaction, 150 mg of bis(2-cyanoethyl) phenylphosphine was added; 60 After 10 minutes, weigh 150 mg of solid sodium borohydride, add 5 mL of deionized water to prepare a solution, and directly and quickly add it to the pear-shaped flask. At this time, the solution turns black immediately; Then, the organic solvent was removed by a rotary evaporator, washed with methanol and toluene, respectively, to remove excess ligands and by-products, and finally the product was dissolved In dichloromethane, the n-hexane is diffused into the dichloromethane solution by the method of gas-phase diffusion, and red crystals are obtained after one week, which is the target product.

By X-ray single crystal diffractometer, we obtained the structure of AuCu ₁₄ nanoclusters. The results showed that the AuCu nanoclusters contained 1 Au atom, 14 Cu atoms, 12 4-tert-butylthiophenol ligands and 6 triphenylphosphine ligands (Fig. 1). In addition, a SbF ₆ -counterion was found at the molecular periphery ^of the AuCu ₁₄ nanoclusters. In summary, the molecular formula of the AuCu ₁₄ nanocluster is determined to be [AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₆ ](SbF ₆ ).

The AuCu ₁₄ nanoclusters were dissolved in a dichloromethane:methanol solution of 1:1 (volume ratio) for electrospray mass spectrometry. The results are shown in FIG. 2 , a molecular ion peak was observed at the m/z position of 4367.35 Da, and the corresponding molecular formula was [AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₆ ] ⁺ . In addition, obvious molecular ion peaks were also observed at 4151.27Da, 3935.19Da and 3717.11Da, and the corresponding molecular formulas were [AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₅ ] ⁺ , [AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₄ ] ⁺ and [AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₃ ] ⁺ .

The UV-Vis absorption spectra of AuCu ₁₄ nanoclusters in dichloromethane solution were measured. The AuCu ₁₄ crystal was dissolved in dichloromethane, and its UV-Vis absorption spectrum showed three distinct absorption peaks at 410 nm, 455 nm and 515 nm, as shown in Figure 3.

The AuCu ₁₄ nanoclusters exhibited good photoluminescence properties. Figure 4 shows the fluorescence spectra of AuCu ₁₄ nanoclusters. The maximum emission wavelength (λ _em ) of AuCu ₁₄ nanoclusters in dichloromethane solution is 625 nm (excitation wavelength is λ _ex = 410 nm), and the maximum emission wavelength (λ _em ) in solid state is 630 nm (excitation wavelength is λ em ) _ex = 410 nm), and its Stokes shift is about 220 nm. Compared with Rhodamine B solution, the relative quantum yield of AuCu ₁₄ nanoclusters in dichloromethane was 71.3%. In addition, Figure 5 shows that the fluorescence emission lifetime of AuCu ₁₄ nanoclusters is 1.23 microseconds, and the luminescence can be quenched by oxygen gas (Figure 6), and the fluorescence can be recovered by nitrogen gas, even stronger than the original luminescence intensity. These results indicate that it has phosphorescent emission behavior.

In the present invention, a direct synthesis method is used to obtain an AuCu nano-cluster with high quantum yield and phosphorescence emission behavior—[AuCu ₁₄ (C ₁₀ H ₁₃ S) ₁₂ (C ₁₂ H ₁₃ N ₂ P) ₆ ](SbF ₆ ). The synthesis method of the cluster is relatively simple, and its precise structure can be characterized by X-ray single crystal diffractometer. In addition, the AuCu ₁₄ nanoclusters exhibited good phosphorescence properties.

Description of drawings

Figure 1 is a schematic diagram of the structure of AuCu ₁₄ nanoclusters.

Figure 2 is an electrospray mass spectrum of AuCu ₁₄ nanoclusters.

Figure 3 is the UV-Vis absorption spectrum of AuCu ₁₄ nanoclusters.

Figure 4 is the emission spectrum of AuCu ₁₄ nanoclusters.

Figure 5 is the luminescence lifetime curve of AuCu ₁₄ nanoclusters.

Figure ₆ is a graph of the emission curves of AuCu ₁₄ nanoclusters in response to O.

Detailed ways

The present invention will be further described below through specific embodiments.

Example 1: Synthesis of AuCu ₁₄ nanoclusters

The whole preparation process was carried out at room temperature and under stirring at a uniform rotation speed of 1200 rpm. First, 400 microliters of aqueous sodium tetrabromoaurate (0.1 grams per milliliter), 130 mg of tetraoctylammonium bromide, and 15 milliliters of dichloromethane were added to a 100 milliliter pear-shaped flask. After 30 minutes, 150 microliters of 4-tert-butylthiophenol was added to the reaction system; after 60 minutes of reaction, 80 mg of Cu(NO ₃ ) ₂ was dissolved in 5 mL of methanol and added to the above solution; reaction 30 minutes later, 150 mg of bis(2-cyanoethyl) phenylphosphine was added; after 60 minutes, 150 mg of solid sodium borohydride was weighed and added to 5 ml of deionized water to prepare a solution, and then added directly to the pear-shaped flask. At this time, the solution turned black immediately; after the reaction continued to stir for 18 hours, the stirring magnet and the aqueous solution in the reaction system were removed, and 5 ml of methanol solution containing 100 mg of sodium hexafluoroantimonate was added; then, the organic solvent was rotated by rotating Evaporator removal, washing with methanol and toluene for several times to remove excess ligands and by-products, and finally dissolving the product in dichloromethane, using the method of vapor diffusion to diffuse n-hexane into the dichloromethane solution, after one week Red crystals are obtained, which is the target product.

Example 2: Characterization of crystal structure

Take the AuCu ₁₄ nanoclusters obtained in Example 1 for further characterization, and the process is as follows:

光源的Bruker D8 Venture衍射仪收集数据，之后使用APEX 3软件对数据进行积分还原。然后在Olex2软件中使用ShelXT和ShelXL程序对结构进行求解和改进。所有的Au，Cu，N和S原子都是直接发现的，剩余的非氢原子是通过差分傅立叶合成而生成的。所有非氢原子均经过各向异性精修。所有氢原子由几何计算给出位置并进行各向同性精炼。使用PLATON中的SQUEEZE方法从数据中删除由残留溶剂分子产生的电子密度，生成的数据再次经过进一步的完善。详细的晶体数据见下表1。Under an optical microscope, the red crystals were selected, and a crystal with better quality was selected for testing under the protection of nitrogen atmosphere (170K). Equipped with Ga-Kα

The data were collected on a Bruker D8 Venture diffractometer at the light source and then integrated using APEX 3 software. The structures were then solved and refined using the ShelXT and ShelXL programs in the Olex2 software. All Au, Cu, N and S atoms were found directly, and the remaining non-hydrogen atoms were generated by differential Fourier synthesis. All non-hydrogen atoms are anisotropically refined. All hydrogen atoms were given positions by geometric calculations and isotropically refined. Electron densities resulting from residual solvent molecules were removed from the data using the SQUEEZE method in PLATON, and the resulting data were again further refined. Detailed crystal data are shown in Table 1 below.

Table 1 Main crystallographic data of AuCu ₁₄ nanoclusters

The above embodiments are only used to illustrate the content of the present invention, in addition to this, the present invention has other embodiments. However, all technical solutions formed by equivalent replacement or equivalent deformation all fall within the protection scope of the present invention.

Claims (3)

1. AuCu with high phosphorescence quantum yield in air atmosphere₁₄Nanoclusters characterized by:

the AuCu₁₄The nanocluster is an AuCu alloy nanocluster protected by mixed ligands, and comprises 1 Au atom, 14 Cu atoms, 12 4-tert-butyl thiophenol ligands and 6 bis (2-cyanoethyl) phenylphosphine ligands, and the periphery of the nanocluster is provided with an SbF₆ ^-A counterion; the AuCu₁₄The precise structure of the nanocluster contains an Au atomic core and a metal cage consisting of 14 cu (i) atoms.

2. AuCu according to claim 1₁₄Nanoclusters characterized by:

the AuCu₁₄The molecular formula of the nanocluster is [ AuCu ]₁₄(C₁₀H₁₃S)₁₂(C₁₂H₁₃N₂P)₆](SbF₆) Abbreviated as AuCu₁₄Belongs to the triclinic system, the space group is P-1,

α＝83.358(7)°，β＝62.415(6)°，γ＝65.215(6)°，

3. a method for preparing an AuCu nanocluster according to claim 1 or 2, comprising the steps of:

firstly, adding a tetrabromo-gold sodium aqueous solution, tetraoctyl ammonium bromide and dichloromethane into a flask, and adding 4-tert-butyl thiophenol into a reaction system after 30 minutes; after 60 minutes of reaction, Cu (NO) was added₃)₂Dissolving in methanol and adding into a reaction system; after reacting for 30 minutes, adding bis (2-cyanoethyl) phenylphosphine; after 60 minutes, weighing sodium borohydride solid, adding deionized water to prepare a solution, directly and quickly adding the solution into the pear-shaped flask, and then immediately turning black the solution; after the reaction is continuously stirred for 18 hours, stirring magnetons and aqueous solution in the reaction system are removed, and methanol solution dissolved with sodium hexafluoroantimonate is added; and then removing the organic solvent by a rotary evaporator, washing by using methanol and toluene respectively to remove redundant ligand and byproducts, finally dissolving the product in dichloromethane, diffusing n-hexane into dichloromethane solution by using a gas phase diffusion method, and obtaining red crystals after one week, namely the target product.

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