Luminescent Cu11 nanocluster with precise atomic structure and preparation method thereof

Abstract

The invention belongs to the technical field of precise chemical synthesis of nano-molecules, and particularly relates to an atomic structure precise type light-emitting Cu11 nano-cluster which can be simply, conveniently and rapidly prepared in a macroscopic quantity and a preparation method of the atomic structure precise type light-emitting Cu11 nano-cluster. The invention provides Cu11 (I) co-protected by cyclohexanethiol and a bis (diphenylphosphine) methane ligand. The three types of Cu11 provided by the invention are Cu clusters co-protected by mixed ligands, and comprise 11 Cu atoms, 9 cyclohexanethiol ligands and 3 bidentate phosphorus ligands, and two NO3 <-> anions are arranged on the periphery of the Cu clusters; the precise structure of the Cu11 is composed of a double-pyramid Cu5 unit similar to a double-triangular pyramid and three Cu2S3P2 elements. Compared with a reported luminescent Cu nanocluster synthesis method, the synthetic method disclosed by the invention has the advantages of simplicity, convenience, quickness, high yield, easiness in crystallization, high universality and the like; and the luminous intensity and the emission center of the Cu11 cluster can be effectively regulated and controlled based on the method.

Description

Technical Field

[0001] The present invention belongs to the technical field of precise chemical synthesis of nano-molecules. Specifically, it relates to a precisely structured luminescent Cu 11 nano-cluster that can be prepared simply, quickly, and in large quantities, and a preparation method thereof. Background Art

[0002] In recent years, metal nano-clusters have attracted the attention of many scientific researchers due to their unique physical and chemical properties. Among them, photoluminescence is one of their important properties. Research results show that the photoluminescence of metal nano-clusters has the following characteristics: strong photostability, good biocompatibility, low toxicity, large Stokes shift, etc. These characteristics make luminescent metal nano-clusters have good application prospects in the fields of bioimaging, biological probes, anti-counterfeiting, and optical devices. Therefore, developing a general method for simply and conveniently preparing metal nano-clusters with high quantum yields in batches has become one of the hotspots pursued by current nano-scientists.

[0003] In the prior art, the luminescent metal nano-clusters are mainly gold nano-clusters, which are costly and not suitable for large-scale popularization and application. In contrast, copper nano-clusters also have luminescent properties comparable to those of gold nano-clusters, and at the same time have the advantages of rich raw material reserves and low economic cost. They have unique advantages in developing inexpensive and high-performance luminescent materials and have important research value. Therefore, it is particularly important to develop a simple, quick, and large-scale preparation method for precisely structured luminescent Cu nano-clusters and to find a general synthesis method. Summary of the Invention

[0004] The present invention provides a precisely structured luminescent Cu 11 nano-cluster that can be synthesized simply, quickly, and in large quantities. The Cu 11 nano-cluster exhibits good photoluminescence performance in air.

[0005] The present invention also provides a preparation method for the above-mentioned precisely structured luminescent Cu 11 nano-cluster. Compared with the reported synthesis methods for luminescent Cu nano-clusters, it is more simple, general, has a high yield, and is easy to crystallize.

[0006] The technical solution adopted by the present invention to achieve the above object is as follows: The present invention provides a precisely structured luminescent Cu 11 nano-cluster, wherein the Cu 11 is a mixed-ligand protected Cu nano-cluster, containing 11 Cu atoms, 9 thiol ligands, and 3 bidentate phosphorus ligands, and is peripherally equipped with two NO3 - anions; the Cu 11The exact structure consists of a double-pyramid Cu5 unit similar to a double triangular pyramid and three Cu2S3P2 motifs.

[0007] Furthermore, the Cu 11 nanocluster is specifically Cu 11 (I), Cu 11 (II), Cu 11 (III); The Cu 11 (I) nanocluster has the molecular formula [Cu 11 (C6H 11 S)9(C 25 H 22 P2)3](NO3 - )2; The Cu 11 (II) nanocluster has the molecular formula [Cu 11 (C6H 11 S)9(C 26 H 24 P2)3](NO3 - )2; The Cu 11 (III) nanocluster has the molecular formula [Cu 11 (C6H 11 S)9(C 34 H 28 P2Fe)3](NO3 - )2.

[0008] Furthermore, Cu 11 (I) nanocluster belongs to the hexagonal crystal system, with the space group P63 / m, a = 19.1893(9), b = 19.1893(9), c = 21.4192(10), α = 90°, β = 90°, γ = 120°; The Cu 11 (II) nanocluster belongs to the triclinic crystal system, with the space group P21 / n, a = 18.7979(18), b = 23.604(2), c = 32.951(3), α = 90°, β = 91.187(3)°, γ = 90; The Cu 11 (III) nanocluster belongs to the triclinic crystal system, with the space group P21 / n, a = 22.208(3), b = 21.746(2), c = 38.374(5), α = 90°, β = 90.243(4)°, γ = 90°.

[0009] The present invention also provides a preparation method for the above-mentioned atomically precisely structured luminescent Cu 11 nanoclusters, which includes the following steps: (1) Add copper nitrate to an anhydrous ethanol solution, stir and dissolve it to obtain a blue clear and transparent solution; (2) Add a bidentate phosphorus ligand to the transparent solution. After reacting for a period of time, a suspension is obtained; (3) Add cyclohexanethiol to the suspension for reaction. After centrifuging and washing the reaction solution, the product is obtained.

[0010] Further, in step (1), the ratio of the absolute ethanol to copper nitrate is 1 mL: 10 - 15 mg.

[0011] Further, in step (2), the molar ratio of copper nitrate to the bidentate phosphorus ligand in the transparent solution is 1: 0.5 - 1: 3.

[0012] Further, in step (2), the bidentate phosphorus ligand is bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane, or 1,1'-bis(diphenylphosphino)ferrocene.

[0013] Further, in step (2), the reaction time is 15 - 60 min.

[0014] Further, in step (3), the molar ratio of copper nitrate to cyclohexanethiol is 1: 0.5 - 1: 3.

[0015] Further, in step (3), the reaction time is 15 - 60 min.

[0016] The present invention provides a general method for preparing Cu co-protected by cyclohexanethiol and a bidentate phosphorus ligand 11 (corresponding to [Cu 11 (I)] for bis(diphenylphosphino)methane, [Cu 11 (II)] for 1,2-bis(diphenylphosphino)ethane, and [Cu 11 (III)] for 1,1'-bis(diphenylphosphino)ferrocene). The three kinds of Cu prepared by the present invention 11 are all Cu nanoclusters protected by co-ligands, containing 11 Cu atoms, 9 thiol ligands, and 3 bidentate phosphorus ligands, with two NO3 - anions on the periphery; the precise structure of the Cu 11 is composed of a double-pyramid Cu5 unit similar to a double triangular pyramid and 3 Cu2S3P2 motifs.

[0017] Compared with the existing synthesis methods, the method mentioned in the present invention has the following advantages: (1) In the existing methods for preparing metal nanoclusters, it is usually necessary to add reducing agents such as NaBH4 for reaction, while this preparation method does not require the addition of reducing agents, and the reaction steps are fewer. The reaction can be completed in about 1 hour.

[0018] (2) The preparation method provided by the present invention can synthesize luminescent Cu in batches 11Nanoclusters, and can also achieve the effective regulation of the luminescence intensity and emission center of Cu 11 nanoclusters. Moreover, the Cu 11 nanoclusters obtained by this method are easy to crystallize, and the crystallization conditions are simple and the time is short.

[0019] (3)The Cu 11 nanoclusters prepared by this method show excellent photoluminescence properties in the air atmosphere at room temperature, and are expected to be used in practical application fields such as sensing, X-ray scintillator imaging and anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 are the structural schematic diagrams of three kinds of Cu 11 nanoclusters. Among them, a is Cu 11 (I), b is Cu 11 (II), c is Cu 11 (III); Figure 2 are the electrospray mass spectra of three kinds of Cu 11 nanoclusters. Among them, a is Cu 11 (I), b is Cu 11 (II), c is Cu 11 (III); Figure 3 are the emission spectra of three kinds of Cu 11 nanoclusters. Among them, a is Cu 11 (I), b is Cu 11 (II), c is Cu 11 (III); DETAILED DESCRIPTION OF THE INVENTION The present invention will be further described below through specific embodiments.

[0021] The three kinds of Cu 11 nanoclusters provided by the present invention have the following molecular formulas: Cu 11 (I) The molecular formula of the nanocluster is [Cu 11 (C6H 11 S)9(C 25 H 22 P2)3](NO3 - )2, belonging to the hexagonal crystal system, the space group is P63 / m, a = 19.1893(9), b = 19.1893(9), c = 21.4192(10), α = 90°, β = 90°, γ = 120°.

[0022] Cu 11 (II) The molecular formula of the nanocluster is [Cu 11 (C6H 11 S)9(C26 H 24 P2)3](NO3 - )2, belonging to the triclinic system, space group P21 / n, a = 18.7979(18), b = 23.604(2), c = 32.951(3), α = 90°, β = 91.187(3)°, γ = 90°.

[0023] Cu 11 (III) The molecular formula of the nanocluster is [Cu 11 (C6H 11 S)9(C 34 H 28 P2Fe)3](NO3 - )2, belonging to the triclinic system, space group P21 / n, a = 22.208(3), b = 21.746(2), c = 38.374(5), α = 90°, β = 90.243(4)°, γ = 90°.

[0024] The present invention provides a general method for simply, quickly, and macroscopically synthesizing luminescent Cu nanoclusters with precise structures. Under room temperature conditions, Cu 11 (I), Cu 11 (II), Cu 11 (III) The specific preparation methods are as follows: Cu 11 (I): (1) Add copper nitrate to an anhydrous ethanol solution, stir and dissolve it to obtain a blue clear and transparent solution.

[0025] (2) Add the bidentate phosphorus ligand - bis(diphenylphosphino)methane to the solution. After reacting for 15 minutes, a grass-green suspension is obtained. (The molar ratio of copper nitrate to bis(diphenylphosphino)methane is 1:1) (3) Add cyclohexanethiol to react, forming a light yellow clear and transparent solution, which then quickly turns into a light yellow precipitate (the molar ratio of copper nitrate to cyclohexanethiol is 1:1).

[0026] (4) Centrifuge, and wash with ethanol (or methanol) and toluene to remove the excess ligands and by-products.

[0027] (5) Dissolve the centrifuged light yellow precipitate in dichloromethane. Use the gas diffusion method to diffuse ethanol into the dichloromethane solution. After three days, golden needle-shaped crystals precipitate, which are the target products; the crystals emit red light under ultraviolet light (365 nm) irradiation.

[0028] Cu 11 (II): (1) Add copper nitrate to an anhydrous ethanol solution, stir and dissolve it to obtain a blue clear and transparent solution.

[0029] (2) Add the bidentate phosphorus ligand - 1,2 - bis(diphenylphosphino)ethane to the solution. After reacting for 15 minutes, a light blue clear and transparent solution is obtained. (The molar ratio of copper nitrate to 1,2 - bis(diphenylphosphino)ethane is 1:1) (3) Add cyclohexanethiol and react for 30 minutes to form a golden yellow clear and transparent solution. (The molar ratio of copper nitrate to cyclohexanethiol is 1:1).

[0030] (4) Centrifuge.

[0031] (5) After centrifugation, the upper layer of the golden yellow clear and transparent solution is left standing at room temperature overnight, and golden yellow block - shaped crystals precipitate, which are the target product; the crystals have strong orange - red luminescence under ultraviolet light (365 nm) irradiation.

[0032] Cu 11 (III): (1) Add copper nitrate to an anhydrous ethanol solution. After stirring and dissolving, a blue clear and transparent solution is obtained.

[0033] (2) Add the bidentate phosphorus ligand - 1,1'-bis(diphenylphosphino)ferrocene to the solution. After reacting for 15 minutes, an orange suspension is obtained. (The molar ratio of copper nitrate to 1,1'-bis(diphenylphosphino)ferrocene is 1:1) (3) Add cyclohexanethiol and react for 30 minutes to form an orange suspension. (The molar ratio of copper nitrate to cyclohexanethiol is 1:1) (4) Centrifuge.

[0034] (5) After centrifugation, the upper layer of the orange clear and transparent solution is left standing at room temperature for 3 days, and orange - yellow prismatic crystals precipitate, which are the target product. The crystals have no visually observable luminescence under ultraviolet light (365 nm) irradiation.

[0035] Example 1: Cu 11 Synthesis of Cu Nanoclusters Cu 11(I): The entire preparation process was carried out under stirring at a uniform rotation speed of 800 rpm at room temperature. First, 241.6 mg of Cu(NO3)2·3H2O and 20 mL of absolute ethanol were added to a 50 mL pear-shaped flask. After stirring and dissolving, a blue clear and transparent solution was obtained. After 15 minutes, 384.39 mg of bis(diphenylphosphino)methane was added to the reaction system to obtain a grass-green suspension; after reacting for 15 minutes, 123 μL of cyclohexanethiol was added to the above solution; after reacting for 30 minutes, a light yellow clear and transparent solution was gradually formed, and then quickly turned into a light yellow precipitate; centrifuged, and the precipitate was washed with ethanol (or methanol) and toluene respectively to remove the excess ligands and by-products. Finally, the product was dissolved in dichloromethane, and ethanol was diffused into the dichloromethane solution by the gas-phase diffusion method. After three days, golden needle-shaped crystals were precipitated, which were the target product; the crystals emitted red light under the irradiation of an ultraviolet lamp (365 nm).

[0036] Cu 11 (II): The entire preparation process was carried out under stirring at a uniform rotation speed of 800 rpm at room temperature. First, 241.6 mg of Cu(NO3)2·3H2O and 20 mL of absolute ethanol were added to a 50 mL pear-shaped flask. After stirring and dissolving, a blue clear and transparent solution was obtained. After 15 minutes, 398.42 mg of 1,2-bis(diphenylphosphino)ethane was added to the reaction system to obtain a light cyan clear and transparent solution; after reacting for 30 minutes, 123 μL of cyclohexanethiol was added to the above solution; after reacting for 30 minutes, a light yellow clear and transparent solution was gradually formed; centrifuged, the golden yellow clear and transparent solution was left standing at room temperature for 24 hours, and then golden yellow block-shaped crystals were precipitated, which were the target product; the crystals emitted red light under the irradiation of an ultraviolet lamp (365 nm).

[0037] Cu 11 (III): The entire preparation process was carried out under stirring at a uniform rotation speed of 800 rpm at room temperature. First, 241.6 mg of Cu(NO3)2·3H2O and 20 mL of absolute ethanol were added to a 50 mL pear-shaped flask. After stirring and dissolving, a blue clear and transparent solution was obtained. After 15 minutes, 384.39 mg of 1,1'-bis(diphenylphosphino)ferrocene was added to the reaction system to obtain an orange suspension; after reacting for 30 minutes, 123 μL of cyclohexanethiol was added to the above solution; after reacting for 30 minutes, an orange suspension was formed; centrifuged, the upper orange clear and transparent solution was left standing at room temperature for 3 days, and then orange-yellow prismatic crystals were precipitated, which were the target product. The crystals did not emit light under the irradiation of an ultraviolet lamp (365 nm).

[0038] Effect Example Take the Cu 11 nanoclusters prepared in Example 1 for further characterization. The process is as follows: Under an optical microscope, crystals were selected, and a crystal with better quality was tested under nitrogen atmosphere protection (170 K). Data were collected on a Bruker D8 Venture diffractometer equipped with a Ga-Kα source, and then the data were integrated and reduced using APEX 3 software. Then, the structure was solved and refined using the ShelXT and ShelXL programs in Olex2 software. All Cu, P, and S atoms were directly located, and the remaining non-hydrogen atoms were generated by difference Fourier synthesis. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed by geometric calculations and refined isotropically. The SQUEEZE method in PLATON was used to remove the electron density generated by residual solvent molecules from the data, and the generated data were further improved. The detailed crystal data of Cu (I), Cu 11 (II), and Cu 11 (III) are shown in Tables 1 - 3 below. 11 (III) See Tables 1 - 3 below for detailed crystal data.

[0039] Table 1 Table 2 Table 3 Through X-ray single crystal diffraction analysis, the structures of Cu 11 (I), Cu 11 (II), and Cu 11 (III) nanoclusters were obtained. The results show that Cu 11 (I), Cu 11 (II), and Cu 11 (III) nanoclusters are all co-ligand protected Cu nanoclusters with similar structures, containing 11 Cu atoms, 9 thiol ligands, and 3 polydentate phosphorus ligands, and are peripherally coordinated with two NO3 - anions; the exact structure of the Cu 11 consists of a double pyramid Cu5 unit similar to a double triangular pyramid and 3 Cu2S3P2 motifs, as shown in Figure 1 . Therefore, the molecular formula of Cu 11 (I), Cu 11 (II), and Cu 11 (III) nanoclusters can be determined to be [Cu 11 (C6H 11 S)9(C 25 H 22 P2)3](NO3 - )2, [Cu 11 (C6H11 S)9(C 26 H 24 P2)3](NO3 - )2, [Cu 11 (C6H 11 S)9(C 34 H 28 P2Fe)3](NO3 - )2, Electrospray ionization mass spectrometry (ESI-MS) tests also confirmed the above conclusion.

[0040] Cu 11 (I)'s ESI-MS results are as Figure 2 shown in a. A molecular ion peak was observed at m / z of 1445.84 Da, and the corresponding molecular formula is [Cu 11 (C6H 11 S)9(C 25 H 22 P2)3] 2- .

[0041] Cu 11 (II)'s ESI-MS results are as Figure 2 shown in b. A molecular ion peak was observed at m / z of 1466.37 Da, and the corresponding molecular formula is [Cu 11 (C6H 11 S)9(C 26 H 24 P2)3] 2- .

[0042] Cu 11 (III)'s ESI-MS results are as Figure 2 shown in c. A molecular ion peak was observed at m / z of 1699.5 Da, and the corresponding molecular formula is [Cu 11 (C6H 11 S)9(C 34 H 28 P2Fe)3] 2- .

[0043] Cu 11 (I), Cu 11 (II), Cu 11 (III) nanoclusters exhibit good photoluminescence properties. Figure 3 Showed the luminescence spectra of Cu 11 (I), Cu 11 (II), Cu 11 (III) nanoclusters.

[0044] Cu 11 (I)'s luminescence spectrum results are asFigure 3 As shown, the maximum emission wavelength (λem) of the nanoclusters in dichloromethane solution is 677 nm (excitation wavelength λex = 265 nm).

[0045] Cu 11 (II)'s luminescence spectrum results are as Figure 3 shown. The maximum emission wavelength (λem) of the nanoclusters in dichloromethane solution is 665 nm (excitation wavelength λex = 265 nm).

[0046] Cu 11 (III)'s luminescence spectrum results are as Figure 3 shown. The nanoclusters have no obvious emission in dichloromethane solution (excitation wavelength λex = 265 nm).

Claims

1. A Cu luminescent material with atomically precise structure 11 Nanoclusters, characterized in that The Cu 11 The mixed ligand-protected Cu nanoclusters contain 11 Cu atoms, 9 thiol ligands, and 3 bidentate phosphorus ligands, with two NO3 - Anion: The Cu 11 The precise structure consists of a double pyramid Cu5 unit similar to a double triangular pyramid and three Cu2S3P2 primitives.

2. The atomic structure precise luminescent Cu according to claim 1 11 Nanoclusters, characterized in that The Cu 11 The nanoclusters are specifically Cu 11 (I), Cu 11 (II), Cu 11 (III); The Cu 11 (I) The molecular formula of the nanocluster is [Cu 11 (C6H 11 S)9(C 25 H 22 P2)3](NO3 - )2; the Cu 11 (II) The molecular formula of the nanocluster is [Cu 11 (C6H 11 S)9(C 26 H 24 P2)3](NO3 - )2; the Cu 11 (III) The molecular formula of the nanocluster is [Cu 11 (C6H 11 S)9(C 34 H 28 P2Fe)3](NO3 - )2.

3. The atomic structure precise luminescent Cu according to claim 2 11 Nanoclusters, characterized in that Cu 11 (I) The nanocluster belongs to the hexagonal system, the space group is P63 / m, a=19.1893(9), b=19.1893(9), c=21.4192(10), α=90°, β=90°, γ=120°; the Cu 11 (II) The nanoclusters belong to the triclinic system, with a space group of P21 / n, a=18.7979(18), b=23.604(2), c=32.951(3), α=90°, β=91.187(3)°, γ=90; the Cu 11 (III) The nanoclusters belong to the triclinic system with space group P21 / n, a = 22.208 (3), b = 21.746 (2), c = 38.374 (5), α = 90°, β = 90.243 (4)°, and γ = 90°.

4. An atomic structure precise luminescent Cu as claimed in any one of claims 1 to 3 11 The method for preparing nanoclusters is characterized in that: The steps include: (1) Add copper nitrate to anhydrous ethanol solution and stir to dissolve to obtain a blue clear and transparent solution; (2) Adding a bidentate phosphorus ligand to the transparent solution and reacting for a period of time to obtain a suspension; (3) Cyclohexanethiol is added to the suspension for reaction, and the reaction solution is centrifuged and washed to obtain the product.

5. The preparation method according to claim 4, characterized in that: In step (1), the ratio of anhydrous ethanol to copper nitrate is 1 mL:10-15 mg.

6. The preparation method according to claim 4 or 5, characterized in that: In step (2), the molar ratio of copper nitrate to bidentate phosphorus ligand in the transparent solution is 1:0.5-1:

3.

7. The preparation method according to claim 4 or 6, characterized in that: In step (2), the bidentate phosphorus ligand is bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane or 1,1'-bis(diphenylphosphino)ferrocene.

8. The preparation method according to claim 7, characterized in that: In step (2), the reaction time is 15-60 min.

9. The preparation method according to any one of claims 4 to 8, characterized in that: In step (3), the molar ratio of copper nitrate to cyclohexyl mercaptan is 1:0.5-1:

3.

10. The preparation method according to claim 2 or 9, characterized in that: The reaction time in step (3) is 15-60 min.

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