An atomically precise binuclear silver nanocluster and a preparation method thereof

Abstract

This invention discloses an atomically precise binuclear silver nanoclusters and its preparation method, belonging to the field of inorganic synthetic chemistry and nanomaterial preparation technology. The method uses a silver salt as a precursor, which is then dissolved in an organic solvent along with another oxidizing metal salt and a phosphorus ligand. Finally, a reducing agent is added to reduce the silver complex. The reaction conditions are mild, the operation is simple, and the yield is high. The binuclear silver nanoclusters of this invention exhibit excellent X-ray scintillator luminescence properties: high X-ray absorption efficiency, high stability, and environmental friendliness, showing promise for future practical applications in X-ray imaging and detection.

Description

Technical Field

[0001] This invention belongs to the field of inorganic synthetic chemistry and nanomaterial preparation technology, and relates to a binuclear silver nanocluster material, its preparation method and application. Background Technology

[0002] Metal nanoclusters, as an emerging nanomaterial, have attracted increasing attention from scientists over the past few decades. Metal nanoclusters are aggregates of several to hundreds of metal atoms, possessing a defined structure and composition, and typically smaller than 2 nm in size. Silver nanoclusters, due to their unique physicochemical properties and good biocompatibility, show broad application prospects in photoluminescence, energy conversion, biomedicine, and chemical sensors. However, the synthesis and application exploration of silver nanoclusters have progressed slowly due to the stringent preparation conditions, poor stability at room temperature, and susceptibility to oxidation. The limited variety of atomically precise silver nanoclusters, coupled with the existing complex preparation methods, hinders research and development in this field. Furthermore, subtle changes in the nanocluster structure can lead to significant changes in properties, highlighting the immense application potential of nanoclusters in certain areas.

[0003] X-ray scintillators are a class of radiation detection materials that can convert high-energy X-rays into low-energy visible light, and are widely used in medical imaging, industrial flaw detection, security inspection, space exploration, and other fields. However, traditional commercial scintillator materials (such as CsI:Tl, Bi4Ge3O) 12 Traditional X-ray scintillator materials (such as PbWO4, YAlO3:Ce, bismuth germanate, and barium fluoride) require large crystals, have demanding preparation conditions, and are costly. Novel perovskite scintillator materials suffer from deliquescence and require the use of highly toxic heavy metals like lead and cesium, causing environmental pollution. In contrast, luminescent Ag2 nanoclusters composed of organic ligands and metals have become a promising candidate for X-ray scintillator materials due to their high X-ray absorption, tunable radiative luminescence, simple preparation, environmental friendliness, and high stability to water and oxygen, attracting widespread attention. Summary of the Invention

[0004] The purpose of this invention is to provide an atomically precise binuclear silver nanocluster and its preparation method. This silver nanocluster exhibits high scintillator luminescence performance under X-ray irradiation, and its precise structure has been obtained.

[0005] To achieve the objectives of this invention, the following technical solution is adopted: The binuclear silver nanoclusters of this invention include Ag nanoclusters, characterized in that: the silver nanoclusters are composed of 2 Ag atoms, 2 bis(diphenylphosphine)methane atoms, and 2 acetate ions. The two Ag atoms are connected to form the core structure of the cluster, and simultaneously, the two Ag atoms are respectively connected and fixed by two bis(diphenylphosphine)methane atoms, forming an octet Ag₂P₄C₂ ring. Furthermore, each Ag atom is coordinated with an oxygen atom in an acetate ion. Since the Ag₂P₄C₂ ring is a non-planar structure, each silver atom is in a highly distorted AgOP₂ triangular planar coordination environment.

[0006] This invention discloses a method for preparing the aforementioned silver nanoclusters, characterized by using a silver salt as a precursor, dissolving it in an organic solvent, then adding a phosphorus ligand and an oxidizing metal salt, and finally reducing the complex with a reducing agent to prepare diatomic silver nanoclusters. Specifically, the method includes the following steps:

[0007] (1) Dissolve the silver salt in an organic solvent.

[0008] (2) Add a certain amount of oxidized metal salt and phosphorus ligand to step (1) at the same time.

[0009] (3) Stir the solution in step (2) at room temperature for a period of time to obtain a blue transparent solution A.

[0010] (4) Dissolve a certain amount of reducing agent in an organic solvent and add it to the blue transparent solution A obtained in step (3). The solution color turns black rapidly. After reacting for a period of time, a black solution B is obtained.

[0011] (5) The black solution B obtained in step (4) is dried by rotary evaporation to obtain black solid C.

[0012] (6) The black solid C obtained in step (5) is washed with a large amount of organic solvent and centrifuged to obtain a colorless and transparent solution D.

[0013] (7) The colorless and transparent single crystals that grow in the colorless and transparent solution D obtained in step (6) with poorly diffused solvent within a certain period of time are the binuclear silver nanoclusters.

[0014] Furthermore, the silver salt mentioned in step (1) is silver acetate, and the organic solvent is ethanol.

[0015] The oxidizing metal salt mentioned in step (2) is copper acetate, and the molar ratio of Ag to Cu atoms is (0.5~1):1.

[0016] The phosphorus ligand mentioned in step (2) is bis(diphenylphosphine)methane, and the molar ratio of silver acetate to bis(diphenylphosphine)methane is (0.1~1):1.

[0017] The stirring rate in step (3) is 400–1000 r / min, and the stirring reaction time is 10–60 min. Ultrasonic acceleration can be used to dissolve the solid.

[0018] The reducing agent mentioned in step (4) is sodium borohydride, the organic solvent is ethanol, and the molar ratio of silver acetate to sodium borohydride is (0.5~2):1.

[0019] The stirring rate in step (4) is 400-1000 r / min, and the stirring reaction time is 1-12 h.

[0020] The rotary evaporation temperature mentioned in step (5) is 30~50℃.

[0021] The organic solvent mentioned in step (6) is dichloromethane.

[0022] The undesirable solvent mentioned in step (7) is pentane or diethyl ether.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] Using silver acetate as the silver source and ethanol as the reaction solvent, the raw materials are readily available and inexpensive.

[0025] The preparation process is simple, reproducible, and yields high levels of wet chemical synthesis at ambient temperature and pressure.

[0026] The cluster exhibits high X-ray absorption by Ag atoms, resulting in strong fluorescence under X-ray irradiation. Furthermore, the silver cluster demonstrates good stability in water and oxygen environments. Attached Figure Description

[0027] Figure 1 This is a crystal structure diagram of Ag2 nanoclusters.

[0028] Figure 2 The image shows the UV-Vis absorption spectrum of Ag2 nanoclusters.

[0029] Figure 3 The excitation emission spectrum is that of a single crystal of Ag2 nanoclusters.

[0030] Figure 4 The X-ray emission spectrum is for Ag2 nanocluster single crystals.

[0031] Figure 5 Photographs of Ag2 nanocluster flexible scintillator films under natural light and ultraviolet light after bending.

[0032] Figure 6The radiative emission spectra of Ag2 nanocluster flexible scintillator films were obtained within different X-ray radiation intensity ranges.

[0033] Figure 7 The functional relationship between the radiative emission intensity of Ag2 nanocluster flexible scintillator film and X-ray dose, and the calculated detection limit are presented.

[0034] Figure 8 The modulation transfer function curve of Ag2 cluster thin films was measured using the X-ray bevel method.

[0035] Figure 9 X-ray scintillator imaging of a small fish using a flexible membrane prepared from Ag2 nanoclusters.

[0036] Figure 10 X-ray imaging of a spring-loaded capsule on a flexible membrane prepared for Ag2 nanoclusters. Detailed Implementation

[0037] The present invention will be further described below through specific embodiments.

[0038] Example 1:

[0039] (1) Add 35 mg silver acetate, 40 mg copper acetate and 70 mg diphenylphosphine to 20 mL of anhydrous ethanol and stir vigorously for 15 min. If there is still a precipitate, use an ultrasonic cleaner to sonicate for a few minutes to accelerate dissolution. The solution turns dark blue.

[0040] (2) Dissolve 20 mg of NaBH4 in 1 mL of anhydrous ethanol by sonication, and quickly add it to the dark blue solution from step (1) above. The solution color quickly turns brown and then black. Stir the mixture at a uniform speed of 600 rpm for 12 h at room temperature.

[0041] (3) After the reaction is complete, the product is dried by rotary evaporation at 50 °C. A large amount of dichloromethane is added to wash the black solid. After centrifugation, the supernatant is obtained. The diethyl ether is diffused into the dichloromethane solution by gas phase diffusion. After one week, a colorless and transparent single crystal is obtained, which is the target product. Example 2:

[0042] (1) Add 35 mg of silver acetate, 20 mg of copper acetate and 50 mg of bis(diphenylphosphine)methane to 20 mL of anhydrous ethanol and stir vigorously for 15 min. If there is still a precipitate, use an ultrasonic cleaner to sonicate for a few minutes to accelerate dissolution. The solution turns dark blue.

[0043] (2) Dissolve 10 mg of NaBH4 in 1 mL of anhydrous ethanol by sonication, and quickly add it to the dark blue solution from step (1) above. The solution color quickly turns brown and then black. Stir the mixture at 1000 rpm for 2 h at room temperature.

[0044] (3) After the reaction is complete, the product is dried by rotary evaporation at 40°C. A large amount of dichloromethane is added to wash the black solid. After centrifugation, the supernatant is obtained. The supernatant is concentrated by rotary evaporation, and a large amount of diethyl ether is added. After shaking and homogenization, a large amount of white powder is rapidly precipitated in the solution, which is the target product. Example 3:

[0045] (1) Add 35 mg of silver acetate, 30 mg of copper acetate and 60 mg of bis(diphenylphosphine)methane to 20 mL of anhydrous ethanol and stir vigorously for 15 min. If there is still a precipitate, use an ultrasonic cleaner to sonicate for a few minutes to accelerate dissolution. The solution turns dark blue.

[0046] (2) Dissolve 20 mg of NaBH4 in 1 mL of anhydrous ethanol by sonication, and quickly add it to the dark blue solution from step (1) above. The solution color quickly turns brown and then black. Stir the mixture at 800 rpm for 6 h at room temperature.

[0047] (3) After the reaction is complete, the product is dried by rotary evaporation at 50°C. A large amount of dichloromethane is added to wash the black solid. After centrifugation, the supernatant is obtained. The pentane is diffused into the dichloromethane solution by gas phase diffusion. After one week, a colorless and transparent single crystal is obtained, which is the target product.

[0048] (4) The silver nanoclusters in this invention are prepared into flexible films through a suitable film-forming process for X-ray imaging. The films exhibit superior performance in terms of flexibility, stability, and X-ray imaging resolution.

[0049] The silver nanoclusters comprise two Ag atoms, two bis(diphenylphosphine)methane (dppm), and two acetate (OAc) ions. The crystal structures of the silver nanoclusters prepared in Examples 1, 2, and 3 are all as described above. Figure 1 As shown. By Figure 1 As can be seen, the core structure of this cluster consists of two bonded Ag atoms, each of which is fixed by two bis(diphenylphosphine)methane atoms, forming an octet Ag₂P₄C₂ ring. Furthermore, each Ag atom is coordinated with an oxygen atom from an acetate ion. Since the Ag₂P₄C₂ ring is non-planar, each silver atom is in a highly distorted triangular-planar coordination environment of AgOP₂.

[0050] Detailed crystal data are shown in Table 1 below.

[0051] Table 1 Crystallographic parameters

[0052]

[0053] Figure 2 The UV-Vis absorption spectrum of Ag2 cluster dissolved in dichloromethane is shown, with two characteristic absorption peaks at 231 nm and 247 nm.

[0054] Figure 3 The excitation and emission spectra of Ag2 cluster single crystals are shown, with the strongest excitation peak and emission peak at 350 nm and 500 nm, respectively.

[0055] Figure 4 The emission spectrum of Ag2 cluster single crystal under X-ray irradiation has a peak at 495 nm, and its spectral range is basically consistent with that of photoluminescence.

[0056] A flexible film was prepared by uniformly dispersing Ag2 clusters in PVA material, such as Figure 5 As shown, the luminescence properties did not change under ultraviolet light, indicating that the clusters were very stable during the preparation process.

[0057] To verify the application prospects of Ag2 single crystal in X-ray scintillators, the prepared flexible thin film was characterized by X-ray imaging. Figure 6 The results show that the Ag2 cluster flexible film exhibits good radioluminescence properties within different dose ranges of X-ray radiation intensity, and the radioluminescence intensity increases linearly with the X-ray dose rate.

[0058] Figure 7 By fitting the relationship between luminescence intensity and radiation dose curve, the lowest detection limit of the scintillator film was calculated to be 585.7 nGy / s, which is more than 9 times lower than the dose used in standard medical diagnosis (5.5 μGy / s).

[0059] Figure 8 An X-ray bevel method was used to image a 1 mm thick sheet of iron with sharp edges, obtaining the modulation transfer function (MTF) curve and determining the spatial resolution of the scintillator to be 11.36 lp mm. -1 .

[0060] Figure 9 , Figure 10 X-ray imaging was performed on a small fish and a capsule containing a metal spring. The images clearly show the skeleton inside the small fish and the X-ray image of the spring inside the capsule, demonstrating the application potential of the film prepared by Ag2 clusters in fields such as bioimaging and non-destructive testing.

[0061] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. However, obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing atomically precise binuclear silver nanoclusters, characterized in that, A binuclear silver nanoclusters were prepared by dissolving a silver salt as a precursor in an organic solvent, then adding a phosphorus ligand and an oxidizing metal salt, and finally reducing the complex with a reducing agent. The specific steps included are as follows: (1) Dissolve the silver salt in an organic solvent; (2) Add a certain amount of oxidizing metal salt and phosphorus ligand to step (1) simultaneously; (3) Stir the solution in step (2) at room temperature for a period of time to obtain a blue transparent solution A; (4) Dissolve a certain amount of reducing agent in an organic solvent and add it to the blue transparent solution A obtained in step (3). The solution color turns black rapidly. After reacting for a period of time, a black solution B is obtained. (5) The black solution B obtained in step (4) is dried by rotary evaporation to obtain black solid C; (6) The black solid C obtained in step (5) is washed with the organic solvent dichloromethane and centrifuged to obtain a colorless and transparent solution D; (7) The colorless and transparent single crystals that grow in the colorless and transparent solution D obtained in step (6) with poorly diffusing solvent pentane or diethyl ether over a period of time are the binuclear silver nanoclusters; the binuclear silver nanoclusters are composed of 2 Ag atoms, 2 bis(diphenylphosphine)methane ligands and 2 acetate ions; the two Ag atoms are respectively connected and fixed by two bis(diphenylphosphine)methanes to form an octet Ag2P4C2 ring; each Ag atom is also coordinated and bonded to an oxygen atom in an acetate ion; The silver salt mentioned in step (1) is silver acetate, and the organic solvent is ethanol; the oxidizing metal salt mentioned in step (2) is copper acetate, and the molar ratio of Ag in the added silver salt to Cu atoms in copper acetate is (0.5~1):1; the phosphorus ligand mentioned in step (2) is bis(diphenylphosphine)methane, and the molar ratio of added silver acetate to bis(diphenylphosphine)methane is (0.1~1):

1.

2. The method as described in claim 1, characterized in that, The stirring rate in step (3) is 400-1000 r / min, and the stirring reaction time is 10-60 min; ultrasonic acceleration is used to dissolve the solid.

3. The method as described in claim 1, characterized in that, The reducing agent mentioned in step (4) is sodium borohydride, the organic solvent is ethanol, and the molar ratio of silver acetate to sodium borohydride is (0.5~2):

1.

4. The method as described in claim 1, characterized in that, The rotary evaporation temperature mentioned in step (5) is 30~50℃.

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