A light-emitting controllable Ag 21 Nanocluster materials and methods for making the same

Abstract

The application discloses a luminescent controllable Ag 21 nanocluster material and a preparation method thereof. The molecular formula of the nanocluster material is [Ag 21 X8L6]Y3 or [Ag 21 X 10 M6]Y, wherein X is a phosphonic acid ligand, L and M are both acetylene ligands containing heterocyclic groups, the heteroatoms of the heterocyclic groups in L include nitrogen atoms and sulfur atoms, the heteroatoms of the heterocyclic groups in M are nitrogen atoms, and Y is a counter anion. The Ag 21 nanocluster material can control luminescent characteristics based on specific ligands, the preparation method is simple, and the cost is low.

Description

Technical Field

[0001] This invention relates to a silver nanocluster material, specifically to a silver nanocluster material with controllable luminescence. 21 The discussion also covers nanocluster materials and their preparation methods, which fall under the technical field of metal nanocluster materials. Background Technology

[0002] Atomic-scale precise metal nanoclusters, due to their ultra-small size, unique electronic structure, and excellent photophysical properties, show broad application prospects in fields such as luminescent materials, bioimaging, chemical sensing, and catalysis. Silver nanoclusters are considered an ideal alternative to gold clusters due to their relatively low cost and excellent optical properties. However, most silver clusters exhibit low luminescence efficiency or even no luminescence at room temperature, mainly because non-radiative transition channels such as vibrational and rotational transitions of the ligands on the cluster periphery are difficult to suppress effectively.

[0003] Ligand engineering is one of the core strategies for controlling the structure and properties of metal clusters. However, most reported ligand control strategies focus on altering the steric hindrance of ligand substituents, and the number of metal nuclei also changes during the control process, leading to changes in the overall properties of the metal cluster and hindering precise control of individual luminescence characteristics. Therefore, developing a silver nanocluster material that can directionally control luminescence characteristics while maintaining a constant number of metal nuclei is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide Ag with controllable luminescence. 21 Nanocluster materials. This silver nanocluster material exhibits controllable luminescence and structural stability.

[0005] The second objective of this invention is to provide Ag with controllable luminescence. 21 A method for preparing nanocluster materials. This method is simple, low-cost, and yields high output.

[0006] To achieve the above technical objectives, the present invention provides a light-controllable Ag... 21 Nanocluster materials with the molecular formula [Ag] 21 X8L6]Y3 or [Ag] 21 X 10 M6]Y, where X is a phosphonic acid ligand, L and M are both alkynyl ligands containing heterocyclic groups, and the heteroatoms of the heterocycle in L include nitrogen and sulfur atoms, the heteroatoms of the heterocycle in M ​​are nitrogen atoms, and Y is a balance anion.

[0007] This invention achieves precise control over the configuration of the 21-nucleus silver cluster metal core by employing alkynyl ligands with different heteroatom coordination abilities, thereby controlling the luminescence properties. The molecular formula is [Ag...]. 21 X10 The M6]Y cluster does not emit light; the nitrogen atom in its heterocycle is not coordinated with Ag, corresponding to the Ag in the cluster. 13 The core is arranged in an icosahedral pattern, and the molecular formula is [Ag]. 21 The X8L6]Y3 cluster contains sulfur atoms in its heterocycles that act as soft bases, coordinating with silver ions of soft acids to drive the Ag in the cluster. 13 The core undergoes a configurational shift, adopting a face-centered cubic (FCC) stacking arrangement. Simultaneously, the rigidity of the entire cluster is enhanced, optimizing both the core electronic structure and the overall structural rigidity, thus improving the [Ag]... 21 The [X8L6]Y3 cluster achieves room-temperature luminescence. This is because the S-Ag coordination bond provides a rigidification effect and an efficient ligand-metal charge transfer channel, thereby strongly suppressing nonradiative transitions, resulting in a fast radiative transition rate and high fluorescence intensity; while [Ag]... 21 X 10 The M6]Y cluster lacks S-Ag secondary coordination bonds, preventing the formation of other effective rigid constraints. Its nitrogen heterocyclic groups (such as carbazole groups) undergo significant torsion or vibration in the excited state. Rapid nonradiative relaxation processes (internal conversion, vibrational relaxation) dissipate excited-state energy, preventing radiative recombination. Theoretical calculations reveal that Ag protected by nitrogen-sulfur heterocyclic-yne ligands (such as phenothiazineyne)... 21 The first excited state is the open state, while Ag protected by nitrogen heterocyclic alkynyl ligands (such as carbazolyne) is... 21 The first excited state is a dark state (the transition dipole moment is almost zero). Although the latter high-energy excited state can be absorbed, it will then rapidly internally convert to the dark state, resulting in no light emission.

[0008] As a preferred embodiment, the Ag 21 The metal core of the nanocluster material consists of 21 silver atoms. Phosphonic acid ligands coordinate with silver atoms in μ5, μ4, μ3 or μ2 coordination modes. Alkyne ligands form σ and π coordination with silver atoms through terminal carbon atoms. When the alkyne ligand contains sulfur atoms, the sulfur atoms form σ coordination with silver atoms.

[0009] As a preferred embodiment, the structural formula of L is: In this ligand, R1 to R8 are all selected from H or alkane groups, with H being more preferred. When R1 to R8 are all H, it is 9-(2-propynyl)phenothiazine, abbreviated as PTH-CH2-C≡C- in this invention. The phenothiazine group in this alkynyl ligand is connected to the alkynyl group through a methylene group. Utilizing the steric effect of the methylene group, the sulfur atom on the phenothiazine group can coordinate with the silver nucleus.

[0010] As a preferred embodiment, the structure of M is as follows: Among them, R9~R 16 All are selected from H or alkane groups, with H being more preferred. When R9~R 16When both are H, it is 9-(2-propynyl)carbazole, which is abbreviated as CZ-CH2-C≡C- in this invention.

[0011] As a preferred embodiment, the structure of the phosphonic acid ligand is as follows: , where R 17 ~R 18 All are selected from phenyl or alkane groups, with phenyl being more preferred.

[0012] As a preferred embodiment, the balancing anion comprises SbF6. - PF6 - BF4 - NO3 - CH3COO - One of them.

[0013] This invention also provides a light-controllable Ag 21 A method for preparing nanocluster materials involves mixing silver salt, phosphonic acid ligand raw materials, acetylene ligand raw materials, and an alkali in a solvent, then adding a reducing agent to carry out a reduction reaction. The resulting reaction product is then recrystallized to obtain the final product.

[0014] As a preferred embodiment, the silver salt includes at least one of AgSbF6, AgPF6, AgBF4, AgNO3, and CH3COOAg.

[0015] As a preferred embodiment, the molar ratio of the phosphine ligand raw material to the silver salt is 1~2:1, and more preferably 1.3~1.8:1.

[0016] As a preferred embodiment, the phosphine ligand raw material is silver phosphonate.

[0017] As a preferred embodiment, the molar ratio of the acetylene ligand raw material to the silver salt is 0.6~1.5:1, and more preferably 0.8~1.2:1.

[0018] As a preferred embodiment, the acetylene ligand raw material is silver acetylene containing sulfur-nitrogen heterocyclic groups or silver acetylene containing nitrogen heterocyclic groups.

[0019] As a preferred embodiment, the structural formula of silver acetylenide containing sulfur-nitrogen heterocyclic groups is as follows: R1 to R8 are all selected from H or alkane groups, with H being more preferred.

[0020] As a preferred embodiment, the structural formula of silver acetylenide containing a nitrogen heterocyclic group is as follows: R9~R 16 All are selected from H or alkane groups, with H being more preferred.

[0021] As a preferred option, the structural formula of silver phosphonate is: R 17 ~R 18 All are selected from phenyl or alkane groups, with phenyl being more preferred.

[0022] As a preferred embodiment, the molar ratio of the alkali to the silver salt is 1 to 3:1.

[0023] As a preferred embodiment, the base is triethylamine.

[0024] As a preferred embodiment, the molar ratio of the reducing agent to the silver salt is 0.1 to 0.3:1.

[0025] As a preferred embodiment, the reducing agent includes at least one of sodium borohydride solution and tert-butylamine borane solution. The concentration of the reducing agent is preferably 0.01~0.06 mol / L.

[0026] As a preferred embodiment, the solvent includes at least one of dichloromethane, chloroform, methanol, ethanol, and acetonitrile.

[0027] As a preferred embodiment, the reduction reaction conditions are: a temperature of -30℃ to 0℃, more preferably -25℃ to -10℃, and a time of 0.5h to 4h, more preferably 0.5h to 1.5h. Controlling the reduction reaction conditions within a suitable range is beneficial for regulating the nucleation and growth kinetics of clusters and improving Ag... 21 Purity and yield of nanocluster materials.

[0028] As a preferred embodiment, the recrystallization method is liquid-phase diffusion crystallization. This recrystallization method is beneficial for obtaining high-quality single-crystal products with high diffraction capabilities.

[0029] The Ag provided by this invention 21 Nanoclusters, based on their controllable luminescence, can be applied to fields such as sensors, optoelectronic devices, and biological imaging.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) This invention precisely regulates Ag through specific ligands. 21 The luminescence properties of nanocluster materials are specifically achieved by controlling the presence or absence of sulfur in the heterocyclic groups of the acetylene ligands to regulate Ag. 21 The luminescence properties of nanoclusters are observed when sulfur is present in the heterocyclic groups of the acetylene ligand. Sulfur coordinates with silver, driving a configurational transformation of the silver nucleus and enhancing the rigidity of the cluster structure. This effectively suppresses the nonradiative vibrational relaxation of the ligand and the metal core, activating luminescence. Conversely, when sulfur is absent from the heterocyclic groups of the acetylene ligand, Ag... 21Nanocluster materials do not emit light, but rather utilize heteroatom coordination to drive configurational transformation, enabling the emission switch to be achieved while maintaining the same number of metal nuclei. This promotes technological development in fields such as bioimaging, novel displays, and even anti-counterfeiting and sensing.

[0032] (2) Ag of the present invention 21 Nanoclusters have stable structures, simple preparation methods, low cost, and high yield. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1 Ag of the present invention 21 A schematic diagram of the single crystal structure of -PTH.

[0035] Figure 2 Ag of the present invention 21 A schematic diagram of the single crystal structure of -CZ.

[0036] Figure 3 Ag of the present invention 21 Solid-state fluorescence spectrum of -PTH nanoclusters.

[0037] Figure 4 Ag of the present invention 21 -PTH and Ag 21 XPS spectrum of -CZ nanoclusters (Ag 3d).

[0038] Figure 5 Ag of the present invention 21 -PTH and Ag 21 Liquid UV-Vis absorption spectrum of -CZ nanoclusters.

[0039] Figure 6 Ag of the present invention 21 -PTH and Ag 21 Solid-state UV-Vis absorption spectrum of -CZ nanoclusters.

[0040] Figure 7 Ag of the present invention 21 -DPV test image of PTH nanoclusters.

[0041] Figure 8 Ag of the present invention 21 -DPV test image of CZ nanoclusters.

[0042] Figure 9 Ag of the present invention 21 -PTH and Ag 21 -CZ nanoclusters modified electrodes under illumination transient photocurrent response curves.

[0043] Figure 10 Ag of the present invention 21 -PTH and Ag 21 Electrochemical impedance spectroscopy of electrodes modified with CZ nanoclusters.

[0044] Figure 11 Ag of the present invention 21 -PTH and Ag 21 - Comparison of room temperature luminescence of CZ nanoclusters. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] In the following examples, AgO2PPh2 (silver diphenylphosphonate), PTH-CH2-C≡CAg (silver phenothiazine-propyne), and CZ-CH2-C≡CAg (silver carbazole-propyne) were all prepared in-house. The carbazole-propyne and phenothiazine-propyne were prepared according to the literature "A, Alisha Rani, et al. 'Quick CuAAC' Chemistry for Hg(II) and Mn(II) ionsensing via 9H-carbazole derivatives." Inorganica Chimica Acta (2021).” AgO2PPh2 (silver diphenylphosphonate), PTH-CH2-C≡CAg (phenthiazide-silver propyne) and CZ-CH2-C≡CAg (carbazole-silver propyne) were prepared according to the literature “He, Rui Lin, et al. . Large Scale Synthesis of a Stable Prefunctionalized Silver Nanocluster.” Angewandte Chemie International Edition 63.40(2024):7.” was prepared.

[0047] The main data and characterization diagrams involved in this invention are presented using the following instruments and equipment:

[0048] Single crystal structure: Single crystal X-ray diffractometer (D8 QUEST, BRUKER).

[0049] Fluorescence spectroscopy: Steady-state transient fluorescence spectrometer (FLS1000, Edinburgh, UK).

[0050] Liquid UV-Vis absorption spectrum: UV-Vis spectrophotometer (UV-1900i, Shimadzu Corporation);

[0051] Solid UV-Vis absorption spectrum: UV-Vis diffuse reflectance spectrometer (UV-2600i, Shimadzu Corporation);

[0052] XPS spectrum: X-ray photoelectron spectroscopy (Thermo Kalpha, Thermo Fisher Scientific).

[0053] DPV test plot and transient photocurrent response curve: Electrochemical workstation (CHI-760E, Shanghai Chenhua Instrument Co., Ltd.).

[0054] Example 1

[0055] A type of Ag 21 The preparation method of nanocluster materials includes the following steps:

[0056] AgSbF6 (0.12 mmol, 41.4 mg), AgO2PPh2 (silver diphenylphosphonate, 0.20 mmol, 65.8 mg), and PTH-CH2-C≡CAg (0.12 mmol, 41.4 mg) solid were added to 12 mL of a mixed solvent of dichloromethane and methanol (volume ratio 5:1). The mixture was stirred to form a pale yellow suspension. 20 μL of triethylamine was added, and the solution was transferred to a reactor at -20 °C. Reduction was initiated by adding 1 mL of 0.015 mmol / mL NaBH4 ethanol solution. The solution color gradually deepened. After reacting for 1 hour, the solvent was evaporated under reduced pressure. The resulting crude solid product was dissolved in 8 mL of dichloromethane, and the supernatant was collected after centrifugation. The supernatant was divided into four equal portions, each subjected to liquid-phase diffusion crystallization with n-hexane. After approximately one week, yellow blocky crystals precipitated, which was Ag. 21 Nanocluster materials with the molecular formula [Ag] 21 (O2PPh2)8(PTH-CH2-C≡C)6](SbF6)3, abbreviated as Ag 21 -PTH.

[0057] The cluster structure was analyzed by X-ray single-crystal diffraction. Its unit cell parameters were: a = 30.698(3) Å, b = 19.283(2) Å, c = 41.908(4) Å, α = 90°, β = 90°, γ = 90°, belonging to an orthorhombic crystal system. Its single-crystal structure is as follows: Figure 1As shown in the figure, Ag 21 In -PTH, there is a significant coordination interaction between the sulfur atom of the phenothiazine group and the silver atom, with the Ag-S bond length being approximately 2.49-2.51 Å. The silver core Ag of this cluster... 13 It is stacked in a face-centered cubic (FCC) manner.

[0058] Example 2

[0059] A type of Ag 21 The preparation method of nanocluster materials includes the following steps:

[0060] AgSbF6 (0.12 mmol, 41.4 mg), AgO2PPh2 (silver diphenylphosphonate, 0.20 mmol, 65.8 mg), and CZ-CH2-C≡CAg (0.12 mmol, 37.4 mg) solid were added to 12 mL of a mixed solvent of dichloromethane and methanol (volume ratio 5:1). The mixture was stirred to form a pale yellow suspension. 20 μL of triethylamine was added, and the solution was transferred to a reactor at -20 °C. Reduction was initiated by adding 1 mL of 0.015 mol / L NaBH4 ethanol solution. The solution color gradually deepened. After reacting for 1 hour, the solvent was evaporated under reduced pressure. The resulting crude solid product was dissolved in 8 mL of dichloromethane, and the supernatant was collected after centrifugation. The supernatant was divided into four equal portions, each subjected to liquid-phase diffusion crystallization with n-hexane. After approximately one week, yellow blocky crystals precipitated, which was Ag. 21 Nanocluster materials with the molecular formula [Ag] 21 (O2PPh2) 10 [(CZ-CH2-C≡C)6](SbF6), abbreviated as Ag 21 -CZ.

[0061] The cluster structure was analyzed by X-ray single-crystal diffraction. Its unit cell parameters were: a = 19.8079(12) Å, b = 26.6414(17) Å, c = 22.0410(15) Å, α = 90°, β = 102.458(2)°, γ = 90°, belonging to the monoclinic crystal system. Its single-crystal structure is as follows: Figure 2 As shown in the figure, Ag 21 -CZ's metallic core and Ag 21 There are significant differences in -PTH; the carbazole group in the CZ ligand contains only a nitrogen atom and has no sulfur coordination, forming Ag... 13 + Composed of two Ag4 cores, including a silver Ag core 13 It is arranged in an icosahedral pattern.

[0062] For Ag 21 -PTH and Ag 21 Solid-state fluorescence analysis of -CZ nanoclusters is shown in Table 1.

[0063]

[0064] As shown in Table 1, the coordination of sulfur atoms in the PTH ligands drove the configurational transformation of the silver nucleus, successfully activating the cluster's room-temperature luminescence; while the CZ cluster, lacking sulfur coordination, did not emit light. This result demonstrates that Ag can be activated through the difference in coordination behavior of heteroatoms in the ligands. 21 Precise "on-off" control of the luminescence properties of nanoclusters.

[0065] Sulfur coordination drives Ag 21 The metallic core of the -PTH nanoclusters underwent a configurational rearrangement, forming a structure different from that of Ag. 21 -The metallic framework arrangement of CZ nanoclusters. From Figure 3 As can be seen from the solid-state fluorescence spectrum, Ag 21 -PTH exhibits a distinct emission peak at 642 nm at room temperature; however, Ag was not detected at room temperature. 21 -CZ fluorescence.

[0066] Figure 4 Ag of the present invention 21 -PTH and Ag 21 XPS spectra of -CZ nanoclusters (Ag 3d) show that Ag... 21 -PTH's Ag 3d 5 / 2 With Ag 3d 3 / 2 The binding energies are located at 368.7 eV and 374.7 eV, respectively, for Ag. 21 -CZ's Ag 3d 5 / 2 With Ag 3d 3 / 2 The binding energies are located at 368.2 eV and 374.2 eV, respectively, indicating that silver species with +1 and 0 valences exist simultaneously in both clusters. This valence distribution characteristic is consistent with the electronic structure and coordination environment information obtained from single crystal structure analysis.

[0067] Figure 5 Ag of the present invention 21 -PTH and Ag 21 The liquid UV-Vis absorption spectrum of -CZ nanoclusters shows that Ag... 21 The absorption peak of -PTH is mainly concentrated at 414 nm, Ag 21 -CZ has three distinct absorption peaks at 326 nm, 339 nm and 447 nm.

[0068] Figure 6 Ag of the present invention 21 -PTH and Ag 21The solid UV-Vis absorption spectrum of the -CZ nanoclusters shows that both types of clusters have good light absorption capabilities in the visible light region.

[0069] Figures 7-8 The Ag of the present invention 21 -PTH、Ag 21 -DPV test results for CZ nanoclusters. The figure shows that Ag... 21 The electrochemical band gap of -PTH is 1.90 eV, Ag 21 -CZ has an electrochemical bandgap of 1.78 eV, compared to Ag 21 -PTH has a wider electrochemical bandgap.

[0070] Figure 9 Ag of the present invention 21 -PTH and Ag 21 The transient photocurrent response curves of electrodes modified by -CZ nanoclusters under illumination are shown in the figure. From the figure, it can be seen that Ag... 21 -PTH photocurrent density is significantly higher than Ag 21 -CZ indicates that its photogenerated carrier separation efficiency is significantly better.

[0071] Figure 10 Ag of the present invention 21 -PTH and Ag 21 -CZ nanoclusters modified the electrodes with electrochemical impedance spectra. As can be seen from the figures, Ag... 21 -PTH has a smaller semicircle diameter in its Nyquist curve, resulting in lower charge transfer resistance, which is beneficial for photogenerated electron transport.

[0072] Figure 11 For Ag 21 -PTH and Ag 21 - A comparison of the luminescence of CZ nanoclusters after irradiation with a UV lamp (365nm) at room temperature. The figure shows that at room temperature, Ag... 21 -PTH nanoclusters emit orange light, while Ag 21 -CZ nanoclusters do not emit light.

[0073] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A luminescent Ag 21 Nanocluster materials, characterized by: Its molecular formula is [Ag] 21 X8L6]Y3 or [Ag] 21 X 10 M6]Y, where X is a phosphonic acid ligand, L and M are both alkynyl ligands containing heterocyclic groups, and the heteroatoms of the heterocycle in L include nitrogen and sulfur atoms, the heteroatoms of the heterocycle in M ​​are nitrogen atoms, and Y is a balance anion.

2. The luminescent Ag according to claim 1 21 Nanocluster materials, characterized by: The structural formula of L is: In this context, R1 to R8 are all selected from H or alkane groups.

3. The luminescent Ag according to claim 1 21 Nanocluster materials, characterized by: The structural formula of M is: Among them, R9~R 16 All are selected from H or alkane groups.

4. The luminescence-controllable Ag according to claim 1 21 Nanocluster materials, characterized by: The structure of the phosphonic acid ligand is as follows: , where R 17 ~R 18 All are selected from phenyl or alkane groups.

5. The luminescent Ag according to claim 1 21 Nanocluster materials, characterized by: The balanced anion includes SbF6. - PF6 - BF4 - NO3 - CH3COO - One of them.

6. A light-controllable Ag as described in any one of claims 1 to 5 21 The method for preparing nanocluster materials is characterized by: Silver salt, phosphonic acid ligand raw material, alkynyl ligand raw material and base are added to solvent and mixed well. Then a reducing agent is added to carry out a reduction reaction. The reaction product is then recrystallized to obtain the final product.

7. A controllable luminescence Ag according to claim 6 21 The method for preparing nanocluster materials is characterized by: The molar ratio of the phosphine ligand raw material to the silver salt is 1~2:1; The molar ratio of the acetylene ligand raw material to the silver salt is 0.6~1.5:1; The molar ratio of the alkali to the silver salt is 1~3:1; The molar ratio of the reducing agent to the silver salt is 0.1 to 0.3:

1.

8. A light-controllable Ag according to claim 6 or 7 21 The method for preparing nanocluster materials is characterized by: The silver salt includes at least one of AgSbF6, AgPF6, AgBF4, AgNO3, and CH3COOAg; The phosphine ligand raw material is silver phosphonate; The acetylene ligand raw material is silver acetylene containing sulfur-nitrogen heterocyclic groups or silver acetylene containing nitrogen heterocyclic groups; The base is triethylamine; The solvent includes at least one of dichloromethane, trichloromethane, methanol, ethanol, and acetonitrile; The reducing agent includes at least one of sodium borohydride solution and tert-butylamine borane solution.

9. A controllable luminescence Ag according to claim 6 21 The method for preparing nanocluster materials is characterized by: The conditions for the reduction reaction are: temperature -30℃ to 0℃, and time 0.5h to 4h.

10. A light-controllable Ag according to claim 6 21 The method for preparing nanocluster materials is characterized by: The recrystallization method is liquid-phase diffusion crystallization.

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