Preparation method of fluorescent silver nanoclusters

Abstract

The application provides a preparation method of fluorescent silver nanoclusters, and solves the problems of complex preparation process, high production cost, and toxic reaction reagents to the environment in the existing preparation method of fluorescent silver nanoclusters, and stable fluorescently labeled silver metal nanoclusters in a low-temperature environment. 11 NiO 39 (H2O)@Ag 48 (CyhS) 24 (p‑TsO) 18 ]·10DMF· i PrOH, and the obtained fluorescent silver nanoclusters have the fluorescent characteristics in a low-temperature environment, and have stable fluorescent behavior in a low-temperature environment of 83K-173K.

Description

Technical Field

[0001] This invention relates to the field of silver nanocluster synthesis, and more specifically to a method for preparing fluorescent silver nanoclusters. Background Technology

[0002] Traditional fluorescent labels, such as rhodamine, fluorescein, piperonine, and phenanthridine dyes, generally suffer from drawbacks including cytotoxicity, poor photostability, narrow excitation spectra, and sensitivity to oxygen. Noble metal nanoclusters, on the other hand, are fluorescent molecular-level aggregates composed of several to tens of atoms of noble metals such as Au, Ag, or Pt. They possess excellent biocompatibility and strong photostability, significantly improving their performance as biomarkers. Currently, noble metal nanoclusters are increasingly being applied in fields such as biosensors, cell labeling and imaging, and biological probes.

[0003] Silver nanoclusters, as a novel fluorescently labeled nanomaterial, have become a research hotspot in academia, leveraging their strong fluorescence properties for biochemical assays. Current traditional methods for preparing fluorescent silver nanomaterials require the use of organic reagents as templates, including DNA, polymers, and dendritic polymers. It is well known that synthesizing these organic templates is typically costly and involves complex processes, especially in the synthesis of DNA and dendritic polymers. Summary of the Invention

[0004] To address the problems of complex preparation processes, high production costs, and the potential for environmental toxicity of the required reaction reagents in existing methods for preparing fluorescent silver nanoclusters, as well as the challenge of achieving stable fluorescent labeling of silver nanoclusters at low temperatures, a method for preparing fluorescent silver nanoclusters for low-temperature environments is provided.

[0005] A fluorescent silver nanocluster, characterized in that the silver metal nanocluster is [SiW 11 NiO 39 (H2O)@Ag 48 (CyhS) 24 (p-TsO) 18 ·10DMF· i PrOH, abbreviated as SiW 11 Ni@Ag 48 Silver nanoclusters;

[0006] The SiW 11 Ni@Ag 48 Silver nanoclusters, belonging to space group P21 / n, with 9 SiW atoms 11 Ni@Ag 48 Molecules aggregate in a unit cell through non-covalent interactions of van der Waals forces;

[0007] 1 SiW11 Ni@Ag 48 The molecule is located at the center of the unit cell, and there are also 8 SiW molecules. 11 Ni@Ag 48 The molecules are distributed at the eight vertices of the unit cell;

[0008] The SiW 11 Ni@Ag 48 Clusters are composed of [SiW 11 NiO 39 (H2O)] 6- Kernel and Ag 48 The core-shell structure composed of the outer shell, the Ag 48 The outer shell consists of 24 CyhS - The ligand and 18 TsO-ligands jointly participate in coordination formation;

[0009] The Ag 48 The frame size of the outer casing is 1.40 × 1.42 × 1.45 nm. 3 ;

[0010] The [SiW] 11 NiO 39 (H2O)] 6- The core is a saturated Keggin structure formed by replacing a WO6 octahedron with the transition metal Ni; the [SiW 11 NiO 39 (H2O)] 6- The kernel is T d Symmetry and with Ag 48 The coincidence of the C3 axis of the outer shell and the symmetry of the core give the outer shell structural stability;

[0011] The [SiW] 11 NiO 39 (H2O)] 6- The core has O atoms with 5 different coordination modes, including 4 bridging oxygen atoms and 11 terminal oxygen atoms with Ag. 48 There are 33 Ag coordinates in the shell, with bond lengths ranging from [missing information].

[0012] The Ag 48 24 CyhS in the outer shell - The cyclohexyl groups of the ligands all adopt a chair configuration. The 18 p-TsO-ion-ligands described there are three different binding modes with silver atoms, namely 6μ3-κ. 1 :κ 1 :κ 1 6μ5-κ 2 :κ 1 :κ 1 6μ2-κ 1 :κ1 :κ 0 The Ag-S bond length ranges from

[0013] The SiW 11 Ni@Ag 48 The Ag···Ag distance in silver nanoclusters is between.

[0014] The simplest formula of the SiW11Ni@Ag48 silver nanoclusters is C 303 H 470 N 10 O 105 SiS 42 NiAg 48 W 11 Elemental analysis (%) measured values: C 25.01, H 3.29, N 0.99, S 9.27, Ni 0.41, Ag 35.58, W 13.93.

[0015] The SiW 11 Ni@Ag 48 The optical band gap of the silver nanoclusters is 1.9 eV.

[0016] The SiW 11 Ni@Ag 48 The preparation method of silver nanoclusters includes the following steps:

[0017] Step 1, Synthesis of (CyhSAg) n Precursor;

[0018] Step 2, Synthesis of K6SiW 11 O 39 Ni(H2O)·xH2O precursor, abbreviated as SiW 11 Ni;

[0019] Step 3, add a certain amount of the (CyhSAg) n Precursor, the K6SiW 11 O 39 Ni(H₂O)·xH₂O and silver methylbenzenesulfonate p-TsOAg are dissolved in a mixed solvent. i In the reaction mixture of PrOH:CH2Cl2:DMF:CH3CN, under light-shielding conditions and at a specific temperature for a certain time, green rhombic crystals are obtained, which are the SiW. 11 Ni@Ag 48 Silver nanoclusters.

[0020] Preferably, in step 3, a certain amount of (CyhSAg) is first added... n The precursor is added to the mixed solventi In PrOH:CH2Cl2:DMF:CH3CN, after thorough mixing, add excess silver methylbenzenesulfonate p-TsOAg and stir until a colorless and transparent solution is formed. Then add an appropriate amount of the aforementioned K6SiW. 11 O 39 Ni(H₂O)·xH₂O produces a green precipitate, which reacts at a specific temperature for a certain time, then volatilizes under light, yielding green rhombic crystals after a certain period, which is the SiW described above. 11 Ni@Ag 48 Silver nanoclusters;

[0021] Preferably, step 1 specifically involves: dissolving an appropriate amount of AgNO3 in CH3CN solution to obtain solution A; dissolving an appropriate amount of CyhSH and Et3N in C2H5OH solution to obtain solution B; slowly adding solution B dropwise to solution A, stirring in the dark, and washing after precipitation to obtain (CyhSAg). n Precursor.

[0022] Preferably, step 2 specifically involves: adding an appropriate amount of K8SiW 11 O 39 xH2O was dissolved in distilled water and heated, then added to an appropriate amount of Ni2SO4 solution. After keeping it at this temperature for a certain period of time, an appropriate amount of KCl was added, which formed a large amount of light green precipitate. After washing the precipitate, it was evaporated and concentrated, and then cooled and crystallized to obtain green elongated crystals.

[0023] Preferably, the mixed solvent in step 3 i The volume ratio of the components PrOH:CH2Cl2:DMF:CH3CN is 20:20:5:4; the volume of the mixed solvent is 4.9 mL.

[0024] Preferably, the specific temperature in step 3 is 65°C.

[0025] Preferably, the "certain time" in step 3 is greater than or equal to 33.3 hours.

[0026] Preferably, the (CyhSAg) n Precursor, the K6SiW 11 O 39 The amounts of Ni(H2O)·xH2O precursor and silver methylbenzenesulfonate p-TsOAg are (CyhSAg) respectively. n :0.0085g, p-TsOAg: 0.0385g, K6SiW 11 O 39 Ni(H2O)·xH2O precursor: 0.0056g.

[0027] For the SiW 11 Ni@Ag48 Silver nanoclusters were subjected to low-temperature fluorescence testing.

[0028] The SiW was further tested. 11 Ni@Ag 48 Fluorescence spectrum of silver nanoclusters at low temperature, the SiW 11 Ni@Ag 48 Silver nanoclusters can emit stable orange fluorescence when excited by ultraviolet light at low temperatures.

[0029] The beneficial effects of this invention are as follows:

[0030] This invention provides a simple and green method for preparing fluorescent silver nanoclusters. The fluorescent silver nanoclusters obtained by this invention exhibit fluorescence characteristics in a low-temperature environment. Compared with other methods, the method of this invention is environmentally friendly, energy-efficient, highly reproducible, requires simple equipment, is low in cost, and is easy to scale up for production. Attached Figure Description

[0031] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0032] Figure 1 This is an embodiment of the present invention (CyhSAg). n Infrared characterization image;

[0033] Figure 2 This is K6SiW in the embodiment of the present invention. 11 O 39 Infrared characterization of Ni(H2O)·xH2O precursor;

[0034] Figure 3 The SiW described in the embodiments of the present invention 11 Ni@Ag 48 Infrared characterization of silver nanoclusters;

[0035] Figure 4 The SiW described in the embodiments of the present invention 11 Ni@Ag 48 Ultraviolet diffuse reflectance test image of silver nanoclusters in solid state;

[0036] Figure 5 The SiW described in the embodiments of the present invention 11 Ni@Ag 48 Temperature-dependent emission spectra of silver nanoclusters at an excitation wavelength of 380 nm;

[0037] Figure 6 The SiW described in the embodiments of the present invention 11Ni@Ag 48 Linear fitting plot of fluorescence emission peak intensity of silver nanoclusters versus temperature;

[0038] Figure 7 The SiW described in the embodiments of the present invention 11 Ni@Ag 48 Structural diagram of silver nanoclusters. Among them, (A)SiW 11 Ni@Ag 48 Complete knot; (B)SiW 11 Ni@Ag 48 Polyacid + Silver Framework; (C)SiW 11 Ni@Ag 48 Silver frame; (D)SiW 11 Ni@Ag 48 Schematic diagram of ligand composition;

[0039] Figure 8 The SiW described in the embodiments of the present invention 11 Ni@Ag 48 Flowchart of silver nanoclusters preparation. Detailed Implementation

[0040] To more clearly illustrate the present invention and to gain a clearer understanding of its technical features, objectives, and beneficial effects, the technical solution of the present invention will now be described in detail below, but this should not be construed as limiting the scope of the present invention.

[0041] Unless otherwise specified, the raw materials, reagents or devices used in the embodiments of the present invention can be obtained from conventional commercial sources or by existing known methods.

[0042] A method for preparing fluorescent silver nanoclusters for low-temperature environments, characterized in that the silver metal nanoclusters are [SiW 11 NiO 39 (H2O)@Ag 48 (CyhS) 24 (p-TsO) 18 10DMF ·i PrOH, abbreviated as SiW 11 Ni@Ag 48 Silver nanoclusters; the preparation method includes the following steps:

[0043] Step 1, Synthesis of (CyhSAg) n Precursor;

[0044] Solution A was obtained by dissolving 5g AgNO3 in 75mL CH3CN solution; solution B was obtained by dissolving 3.67mL CyhSH and 5mL LEt3N in 50-200mL C2H5OH solution; solution B was slowly added dropwise to solution A, stirred in the dark for 3 hours, and the precipitate was washed to obtain (CyhSAg). n Precursor. (CyhSAg) n The precursor was characterized by infrared radiation, such as Figure 1 As shown, a value of 2929cm was found. -1 and 2853cm -1 The absorption peaks are attributed to the antisymmetric and symmetric stretching vibrations of -CH2- in cyclohexylsilver sulfide, respectively. (CyhSAg) n The precursor does not contain the SH vibration band (2535-2570cm). -1 ), (CyhSAg) n The deprotonated state of the precursor is due to coordination between Ag and S, confirming that silver and cyclohexylthiol have fully reacted to form a polymer.

[0045] Step 2, Synthesis of K6SiW 11 O 39 Ni(H2O)·xH2O precursor;

[0046] 2-8g K8SiW 11 O 39 Dissolve in 10-50 mL of distilled water, heat the solution to 30-60 °C, and then add 1-6 mL of 0.3-0.6 mol·L⁻¹ to the solution. -1 In a Ni₂SO₄ solution, after maintaining the temperature at 30-60℃ for 10 minutes, 2-5 g of KCl was added, forming a large amount of pale green precipitate. The precipitate was filtered and washed with large amounts of ethanol and ether. The treated precipitate was dissolved in hot water, evaporated and concentrated, and then cooled to crystallize, yielding green elongated crystals.

[0047] Step 3, add 0.0005-0.05g of the (CyhSAg) n The precursor was added to 10 mL of the mixed solvent. i Mix thoroughly in PrOH:CH2Cl2:DMF:CH3CN i The volume ratio of PrOH:CH2Cl2:DMF:CH3CN is 20:20:5:4. Then, add excess p-TsOAg and stir until a colorless and transparent solution is formed. Finally, add 0.005-0.05g of K6SiW. 11 O 39The Ni(H2O)·xH2O precursor was stirred until a green precipitate formed. The reaction was then carried out at 45-65℃ for a certain time, followed by volatilization under light. After a certain period, green rhombic crystals were obtained, which is the SiW. 11 Ni@Ag 48 Silver nanoclusters.

[0048] For the SiW 11 Ni@Ag 48 Silver nanoclusters were analyzed using a Mo target on a Bruker D8 SMART APEXIICCD X-ray single crystal diffractometer. The crystal structure was determined using the direct method, and the crystallographic data are shown in Table 1.

[0049] Table 1. SiW 11 Ni@Ag 48 Crystallographic data of silver nanoclusters

[0050]

[0051] Regarding the (CyhSAg) n The precursor was characterized by infrared radiation, such as Figure 1 As shown, 2929cm -1 and 2853cm -1 The absorption peaks are attributed to the antisymmetric and symmetric stretching vibrations of -CH2- in cyclohexylsilver sulfide, respectively. (CyhSAg) n The precursor does not contain the SH vibration band (2535-2570cm). -1 The (CyhSAg) n The deprotonated state of the precursor is due to coordination between Ag and S, confirming that silver and cyclohexylthiol have fully reacted to form a polymer.

[0052] For the K6SiW 11 O 39 The Ni(H2O)·17H2O precursor was characterized by infrared spectroscopy, such as Figure 2 As shown.

[0053] For the SiW 11 Ni@Ag 48 The silver nanoclusters were characterized by infrared spectroscopy, such as... Figure 3 As shown. Due to SiW 11 Ni@Ag 48 The Ni and W atoms in SiW are highly disordered and cannot be determined by SXRD. We use FT-IR spectroscopy to further determine the composition of SiW. 11 Ni is encapsulated within Ag 48 Inside the shell. Because SiW 11 In Ni, W is replaced by Ni, at 787 cm⁻¹ -1v as (WO c The absorption peak of ) split into two at 799 cm⁻¹ -1 and 694cm -1 The broad peaks centered on SiW, these characteristic peaks can also be found in SiW 11 Ni@Ag 48 This was observed in the infrared spectrum, indicating that SiW 11 Ni was successfully encapsulated into Ag. 48 Inside the silver casing.

[0054] For the SiW 11 Ni@Ag 48 Solid-state UV diffuse reflectance testing was performed on silver nanoclusters, such as... Figure 4 As shown, the SiW 11 Ni@Ag 48 Silver nanoclusters all possess d 10 The electronically structured Ag(Ⅰ) also lacks a dd absorption band; the SiW 11 Ni@Ag 48 Silver nanoclusters exhibit a wide absorption range for ultraviolet light; the SiW 11 Ni@Ag 48 The position of the ultraviolet absorption peak at 336 nm of silver nanoclusters is due to CyhS - n→π * The absorption in the visible light region caused by electronic transitions is due to charge transfer from the ligand to the metal. By processing solid-state UV data using the Kubelka-Munk equation, the SiW... 11 Ni@Ag 48 The optical bandgap of the silver nanoclusters is 1.90 eV, which represents the value of the SiW... 11 Ni@Ag 48 Silver nanoclusters are a potential narrow bandgap semiconductor.

[0055] For the SiW 11 Ni@Ag 48 Temperature-dependent fluorescence testing was performed on the silver nanoclusters, and the SiW 11 Ni@Ag 48 The temperature-varying emission spectrum of silver nanoclusters at an excitation wavelength of 380 nm is as follows: Figure 5 As shown, the SiW 11 Ni@Ag 48 The fluorescence emission peak of the silver nanoclusters is in the visible light region. When the temperature is reduced from 293K to 83K, the emission peak position shifts from 675nm to 622nm. This is due to the oxidation of CyhS on the silver framework at low temperatures. - The thermal motion of p-TOS-ligands is restricted, which inhibits the proportion of internal silver nucleus transitions.

[0056] For the SiW 11 Ni@Ag 48 The fluorescence emission peak intensity of silver nanoclusters was linearly fitted with temperature, such as... Figure 6 As shown, it conforms to Formula I at 83K-173K. max =-289.02T+51374.26, which conforms to Formula I at 203-293K. max = -14.56T + 4309.93. Between 83K and 173K, the k-value is relatively large at -289.02, meaning that the emission peak intensity changes drastically with temperature in this range. At 83K, SiW was tested using a 375nm exciter as the light source. 11 Ni@Ag 48 The fluorescence lifetime was calculated to be on the order of microseconds, at 1.59 ns, indicating that the SiW... 11 Ni@Ag 48 Silver nanoclusters exhibit stable fluorescence behavior in low-temperature environments of 83-173 K.

Claims

1. A method for preparing fluorescent silver nanoclusters, characterized in that, The silver nanoclusters are [SiW 11 NiO 39 (H2O)@Ag 48 (CyhS) 24 (p-TsO) 18 ·10DMF· i PrOH, abbreviated as SiW 11 Ni@Ag 48 Silver nanoclusters, the SiW 11 Ni@Ag 48 Silver nanoclusters, belonging to space group P21 / n, with 9 SiW atoms 11 Ni@Ag 48 Molecules aggregate in a unit cell through non-covalent interactions of van der Waals forces; the SiW 11 Ni@Ag 48 Silver nanoclusters can emit stable orange fluorescence when excited by ultraviolet light at low temperatures, wherein the low temperature environment is 83-173K. The preparation method includes the following steps: Step 1, Synthesis of (CyhSAg) n Precursor; Step 2, Synthesis of K6SiW 11 O 39 Ni(H2O)·xH2O precursor; Step 3, add a certain amount of the (CyhSAg) n Precursor, the K6SiW 11 O 39 Ni(H₂O)·xH₂O and p-TsOAg are dissolved in a mixed solvent. i In the reaction mixture of PrOH:CH2Cl2:DMF:CH3CN, under light-shielding conditions and at a specific temperature for a certain time, green rhombic crystals are obtained, which are the SiW. 11 Ni@Ag 48 Silver nanoclusters; The specific temperature mentioned in step 3 is 65°C; The specified time in step 3 is greater than or equal to 33.3 hours; The (CyhSAg) mentioned in step 3 n Precursor, the K6SiW 11 O 39 The amounts of Ni(H2O)·xH2O precursor and p-TsOAg are respectively (CyhSAg). n :0.0085g, p-TsOAg: 0.0385g, K6SiW 11 O 39 Ni(H2O)·xH2O precursor: 0.0056g.

2. The method for preparing fluorescent silver nanoclusters according to claim 1, characterized in that, Step 1 specifically involves: dissolving an appropriate amount of AgNO3 in CH3CN solution to obtain solution A; dissolving an appropriate amount of CyhSH and Et3N in C2H5OH solution to obtain solution B; slowly adding solution B dropwise to solution A, stirring in the dark, and washing after precipitation to obtain (CyhSAg). n Precursor.

3. The method for preparing fluorescent silver nanoclusters according to claim 1, characterized in that, Step 2 specifically involves: adding an appropriate amount of K8SiW 11 O 39 xH2O was dissolved in distilled water and heated, then added to an appropriate amount of Ni2SO4 solution. After keeping it at this temperature for a certain period of time, an appropriate amount of KCl was added, which formed a large amount of light green precipitate. After washing the precipitate, it was evaporated and concentrated, and then cooled and crystallized to obtain green elongated crystals.

4. The method for preparing fluorescent silver nanoclusters according to claim 2 or 3, characterized in that, In step 3, a certain amount of (CyhSAg) is first added. n The precursor is added to the mixed solvent i In PrOH:CH2Cl2:DMF:CH3CN, after thorough mixing, add excess p-TsOAg and stir until a colorless and transparent solution is formed. Then add an appropriate amount of the aforementioned K6SiW. 11 O 39 Ni(H₂O)·xH₂O produces a green precipitate, which reacts at a specific temperature for a certain time, then volatilizes under light, yielding green rhombic crystals after a certain period, which is the SiW described above. 11 Ni@Ag 48 Silver nanoclusters.

5. The method for preparing fluorescent silver nanoclusters according to claim 4, characterized in that, The mixed solvent in step 3 i The volume ratio of the components PrOH:CH2Cl2:DMF:CH3CN is 20:20:5:4; the volume of the mixed solvent is 4.9 mL.

6. The method for preparing fluorescent silver nanoclusters according to claim 5, characterized in that, The SiW 11 Ni@Ag 48 The optical band gap of the silver nanoclusters is 1.90 eV.

7. The method for preparing fluorescent silver nanoclusters according to claim 6, characterized in that, The SiW 11 Ni@Ag 48 The fluorescence emission peak intensity of silver nanoclusters conforms to Formula I with respect to temperature in the range of 83K-173K. max =-289.02T+51374.26, which conforms to Formula I in the range of 203K-293K. max = -14.56T + 4309.93.

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