Near-infrared low-potential electrochemiluminescence double-ligand stabilized gold nanoclusters, preparation method and application thereof

Abstract

This invention relates to a near-infrared low-potential electrochemiluminescence dual-ligand stabilized gold nanoclusters, their preparation method, and applications. The method uses chloroauric acid as the gold source and thiomalic acid and sodium citrate as reducing and stabilizing agents, respectively, in a two-step synthesis. First, Au is reduced online using thiomalic acid. 3+ Water-soluble gold nanoclusters were prepared using a novel method. These nanoclusters were then incubated with sodium citrate, and based on the ligand exchange principle, gold nanoclusters co-coated with thiomalic acid and sodium citrate were synthesized. The raw materials required for this invention are readily available and all possess good water solubility. The synthesis apparatus is simple, the conditions are mild, and the operation is safe. The resulting dual-ligand-coated gold nanoclusters exhibit good stability and produce low-potential near-infrared electrochemiluminescence in the long-wavelength region in an aqueous system. This overcomes the limitation of most current electrochemiluminescent materials requiring hydrazine hydrate or carbazide as a co-reactant. Using a non-toxic tert-butylamine-borane co-reactant, low-potential electrochemiluminescence radiation of 0.57V in the near-infrared region was generated.

Description

Technical Field

[0001] This invention relates to a near-infrared low-potential electrochemiluminescence dual-ligand stabilized gold nanoclusters, their preparation method, and applications, belonging to the field of analytical techniques. Background Technology

[0002] Electrochemiluminescence (ECL) is a unique photoluminescence phenomenon produced when an electroexcited luminescent substance transitions from an excited state to its ground state. The characteristics of ECL are determined by both the luminescent substance and the co-reactant. Developing novel ECL systems, specifically matching ECL reagents and co-reactants, has always been crucial in the field of ECL. For example, based on Ru(bpy)3... 2+ Electrochemiluminescence reagent kits and corresponding instruments based on the tri-n-propylamine (TPrA) system have dominated the in vitro diagnostics field both domestically and internationally for many years. Therefore, there is an urgent need to develop novel electrochemiluminescence reagents and matching electrochemiluminescence systems to improve performance. The Bard research group first reported the electrochemiluminescence of Si nanoparticles in 2002 (Science 2002, 296, 1293), and subsequently made a series of advances in the electrochemiluminescence of nanomaterials represented by II-VI quantum dots (Chem. Rev. 2014, 114, 11027). I-VI quantum dots typically contain toxic elements, posing potential environmental and biological toxicity risks. Therefore, the electrochemiluminescence of biocompatible gold, silver, and copper nanoparticles is attracting widespread attention.

[0003] Classic Ru(bpy)3 2+ The electrochemiluminescence potential of the / TPrA system is too high (1.2V vs Ag / AgCl), which easily causes oxidative damage to biochemical samples, which is detrimental to reducing electrochemical interference and improving electrode tolerance. Liu et al. confirmed that CdTe quantum dots on paraffin-impregnated graphite electrodes can produce electrochemiluminescence at a low potential of ~0.89V (vs Ag / AgCl) in the presence of dissolved oxygen (Analyst 2008, 133(9), 1161). Liang et al. found that CdTe quantum dots with dual ligands as stabilizers have two obvious redox ECL processes, with the lowest peak potential being ~0.63V (vs Ag / AgCl) (Anal. Chem. 2012, 84(24), 10645). Some strong reducing chemicals such as hydrazine hydrate and carbazide have been shown to be co-reactants that can produce low-potential electrochemiluminescence (Anal. Chem. 2020, 92(8), 6144; 2019, 91(15), 10221). However, hydrazine hydrate is highly toxic, and the electrochemiluminescence efficiency of the carbazide system is lower than that of the hydrazine hydrate system. However, most electrochemiluminescent materials are currently matched with hydrazine hydrate or carbazide.

[0004] Therefore, developing novel electrochemiluminescent reagents with low hole injection potentials and safe, non-toxic co-reactants with even lower oxidation potentials is of great significance for achieving low-potential electrochemiluminescent radiation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a near-infrared low-potential electrochemiluminescence dual-ligand-stabilized gold nanoclusters, their preparation method, and applications.

[0006] The dual-ligand-stabilized water-soluble gold nanoclusters provided by this invention can generate low-potential near-infrared electrochemiluminescence in the long-wavelength region in an aqueous system under co-reactant conditions, with a maximum emission wavelength exceeding 800 nm and a minimum radiation potential less than 0.60 V.

[0007] This invention is achieved through the following technical solution:

[0008] A near-infrared low-potential electrochemiluminescence dual-ligand-stabilized gold nanoclusters, wherein the gold nanoclusters are co-coated with citrate and thiomalic acid dual ligands and have a spherical morphology with a diameter of 1-5 nm.

[0009] According to a preferred embodiment of the present invention, the aqueous solution of the gold nanocluster material is brownish-yellow, and has a strong absorption peak at 564 nm in the ultraviolet-visible spectrum; the maximum fluorescence emission wavelength is 815 nm, and no obvious fluorescence is visible under ultraviolet light; the maximum wavelength of its electrochemiluminescence is 835 nm.

[0010] The second objective of this invention is to provide a method for preparing the aforementioned near-infrared low-potential electrochemiluminescence dual-ligand-stabilized gold nanoclusters.

[0011] The above-mentioned method for preparing near-infrared low-potential electrochemiluminescence dual-ligand stabilized gold nanoclusters uses chloroauric acid as the gold source. First, thiomalic acid is used as a reducing agent and stabilizer to reduce Au. 3+ A single-ligand-stabilized water-soluble gold nanoclusters were prepared. Then, the single-ligand-stabilized water-soluble gold nanoclusters were mixed with citrate and incubated together to obtain gold nanoclusters stabilized by thiomalic acid and sodium citrate.

[0012] According to a preferred embodiment of the present invention, the preparation method of the near-infrared low-potential electrochemiluminescence dual-ligand-stabilized gold nanoclusters includes the following steps:

[0013] (1) The chloroauric acid (H4AuCl4) solution and the thiomalic acid (MSA) ligand were ultrasonically mixed until homogeneous;

[0014] (2) The solution obtained in step (1) is heated to react and a single-ligand stable water-soluble gold nanoclusters are obtained. The solution changes from colorless to brownish-yellow.

[0015] (3) Add citrate (Cit) to the solution prepared in step (2), mix by sonication, and incubate at room temperature;

[0016] (4) After the reaction is complete, centrifuge to remove the large particles at the bottom, purify the solution with isopropanol, and the resulting precipitate is the gold nanocluster with dual ligands.

[0017] According to the present invention, preferably, in step (1), the molar ratio of gold to thiomalic acid in chloroauric acid is 1:(1-5).

[0018] The most preferred molar ratio of gold to thiomalic acid in chloroauric acid is 1:3.

[0019] According to the present invention, preferably, in step (1), the concentration of the H4AuCl4 solution is 80-100mM.

[0020] According to the present invention, preferably, in step (2), the heating temperature is 90-100℃ and the heating time is 130-150h.

[0021] According to the present invention, preferably, in step (3), the molar ratio of gold in citrate to chloroauric acid is 1:350-500.

[0022] According to the present invention, preferably, in step (3), the incubation time at room temperature is 0.5-3h.

[0023] According to the present invention, preferably, in step (4), isopropanol is purified by adding isopropanol to the solution and centrifuging at 13,000-14,000 rpm.

[0024] A preferred embodiment of the present invention provides a method for preparing infrared low-potential electrochemiluminescence dual-ligand-stabilized gold nanoclusters, comprising the following steps:

[0025] (1) 610-650 μL of 96 mM H4AuCl4 solution and 10-30 mL of 9.6 mM thiomalic acid solution were ultrasonically mixed, and the mixture was heated under reflux at 90-100 °C for 130-150 h to obtain thiomalic acid-coated gold nanoclusters.

[0026] (2) Mix the 0.1-0.3mM citrate solution with the solution obtained in step (1), sonicate to mix, and incubate at room temperature for 1h to obtain gold nanoclusters co-coated with citrate and thiomalic acid to the two ligands.

[0027] (3) The solution obtained in step (2) is purified by centrifugation with isopropanol, and the resulting precipitate is the gold nanocluster with dual ligands.

[0028] The application of the above-mentioned dual-ligand-stabilized water-soluble gold nanoclusters, under the condition of tert-butylamine-borane co-reactant, generates low-potential electrochemiluminescence radiation in the near-infrared region.

[0029] Technical features and advantages of the present invention:

[0030] 1. This invention obtains gold nanoclusters stabilized by thiomalic acid and sodium citrate dual ligands through a two-step method. The prepared gold and silver nanoclusters have the advantages of being free of toxic elements, having good biocompatibility, and being stable in storage.

[0031] 2. The dual-ligand stable gold nanoclusters prepared by this invention can generate low-potential electrochemiluminescence radiation in the near-infrared region in an aqueous system. The maximum emission wavelength is 835 nm, which is greater than 800 nm, and the minimum radiation potential is less than 0.60 V. The preparation method is simple, mild, and safe to operate.

[0032] 3. This invention successfully synthesizes a novel electrochemiluminescent reagent with low hole injection potential. Under the condition of tert-butylamine-borane co-reactant, it can generate low-potential near-infrared electrochemiluminescence in the long-wavelength region in an aqueous system. This overcomes the limitation of most current electrochemiluminescent materials being matched with hydrazine hydrate or carbazide. Using non-toxic tert-butylamine-borane co-reactant, it generates low-potential electrochemiluminescent radiation of 0.57V in the near-infrared region. Attached Figure Description

[0033] Figure 1 The image shows the X-ray energy dispersive spectroscopy (EDS) spectrum of the dual-ligand-stabilized gold nanoclusters prepared in Example 1.

[0034] Figure 2 This is a high-magnification transmission electron microscope image of the dual-ligand-stabilized gold nanoclusters prepared in Example 1.

[0035] Figure 3 The fluorescence spectrum of the dual-ligand-stabilized gold nanoclusters prepared in Example 1 is shown.

[0036] Figure 4 The image shows the ultraviolet spectrum of the dual-ligand-stabilized gold nanoclusters prepared in Example 1.

[0037] Figure 5 The image shows the electrochemiluminescence spectrum of Example 2, with a potential window of 0–1.6 V and a scan rate of 50 mV / s; the horizontal axis represents wavelength and the vertical axis represents electrochemiluminescence intensity.

[0038] Figure 6 The image shows the electrochemiluminescence intensity-(potential) time curve driven by cyclic voltammetry in Example 2; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0039] Figure 7 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 1; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0040] Figure 8 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 2; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0041] Figure 9 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 3; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0042] Figure 10 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 4; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0043] Figure 11 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 5; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0044] Figure 12 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 6; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity.

[0045] Figure 13 The image shows the electrochemiluminescence intensity-(potential)-time curve driven by cyclic voltammetry for Comparative Example 7; the potential window is 0–1.6 V, and the scan rate is 50 mV / s; the horizontal axis represents potential, and the vertical axis represents electrochemiluminescence intensity. Detailed Implementation

[0046] The present invention is further illustrated by the following examples, but is not limited thereto.

[0047] The fluorescence spectra of the gold and silver nanoclusters described in the examples were obtained using an F-4700 fluorescence spectrophotometer.

[0048] The ultraviolet-visible absorption spectra were obtained using an Agilent Cary 60 UV-Vis spectrophotometer.

[0049] Electrochemiluminescence spectra were acquired using the GCFG-A electrochemiluminescence spectroscopy acquisition system developed by Shandong Guochen Biotechnology Co., Ltd. The potential window used was 0–1.6 V, and the scan rate was 50 mV / s.

[0050] Electrochemiluminescence assay: A gold nanocluster-modified electrode was prepared by drop-coating 10 μL of a 2 mg / mL dual-ligand-stabilized gold nanocluster solution onto the surface of a glassy carbon electrode and allowing it to dry. The gold nanocluster-modified electrode was used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt wire as the counter electrode. The test solution was a 0.1 mol / L phosphate buffer solution (pH 7.4) containing 10 mmol / L of different co-reactants. The collected electrochemiluminescence spectra were the integrated spectra of all ECL radiations.

[0051] The vessels used in the examples were soaked in freshly prepared aqua regia for 24 hours, thoroughly rinsed with ultrapure water and ethanol, and then air-dried.

[0052] Example 1

[0053] Preparation of infrared low-potential electrochemiluminescence dual-ligand stabilized gold nanoclusters:

[0054] (1) 625 μL of 96 mM H4AuCl4 solution and 20 mL of 9.6 mM thiomalic acid solution were ultrasonically mixed and added to a three-necked flask. The mixture was then heated under reflux at 95 °C for 144 h to obtain thiomalic acid-coated gold nanoclusters. The solution changed from colorless to brownish-yellow.

[0055] (2) Weigh out 0.15mM sodium citrate solution and mix it with the gold nanoclusters coated with thiomalic acid prepared in step (1), mix them by ultrasonication, the molar ratio of sodium citrate to H4AuCl4 is 1:400, and incubate at room temperature for 1h.

[0056] (3) Isopropanol was added to the solution obtained in step (2), and the precipitate was collected by centrifugation at 13000 rpm to obtain dual-ligand stable gold nanoclusters.

[0057] The X-ray energy dispersive spectroscopy (EDS) spectra of the obtained dual-ligand-stabilized gold nanoclusters are shown in [reference needed]. Figure 1 .

[0058] Experimental Example 1

[0059] 1. The precipitate collected in step (3) of Example 1 was dried into powder. A 1 mg / mL solution prepared from the powder was dropped onto a copper grid to characterize the morphology of the gold nanoclusters. The gold nanoclusters were observed under a high-power transmission electron microscope. Figure 2 .from Figure 2 It can be seen that the dual-ligand-stabilized gold nanoclusters are spherical particles with a diameter of 3 nm.

[0060] 2. The fluorescence spectrum of the dual-ligand-stabilized gold nanoclusters prepared in step (3) of Example 1 was tested, see [see details]. Figure 3 ,from Figure 3 As can be seen, the maximum fluorescence emission wavelength of the prepared dual-ligand gold nanoclusters is located at 815 nm, which is in the near-infrared region.

[0061] 3. The ultraviolet spectrum of the dual-ligand-stabilized gold nanoclusters prepared in step (3) of Example 1 was tested, see [see details]. Figure 4 ,from Figure 4 As can be seen, the prepared dual-ligand gold nanoclusters have a distinct surface plasmon resonance peak at 564 nm.

[0062] Example 2

[0063] Application of the dual-ligand-stabilized water-soluble gold nanoclusters prepared in Example 1:

[0064] The dual-ligand-stabilized gold nanoclusters obtained in step (3) of Example 1 were prepared into a 2 mg / mL dual-ligand-stabilized gold nanocluster solution.

[0065] A 10 μL solution of dual-ligand-stabilized gold nanoclusters was dropped onto the surface of a glassy carbon electrode and dried at room temperature to prepare a gold nanocluster-modified electrode. A three-electrode system was formed, consisting of the gold nanocluster-modified electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt wire as the counter electrode. The system was placed in a 0.1 mol / L phosphate buffer solution (pH 7.4) containing 10 mmol / L tert-butylamine-borane co-reactant. The three-electrode system and cyclic voltammetry were used to drive the electrochemiluminescence radiation of the system, and the electrochemiluminescence spectrum was collected as the integrated spectrum of all ECL radiation.

[0066] The electrochemiluminescence spectrum obtained by cyclic voltammetry is shown below. Figure 5 As shown, from Figure 5 As can be seen from the data, the maximum radiation position of the electrochemiluminescence spectrum of the dual-ligand-stabilized gold nanoclusters prepared in Example 1 is located at 835 nm, which is in the near-infrared region.

[0067] The electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 6 ,from Figure 6 As can be seen from the results, with tert-butylamine-borane as the co-reactant, the maximum electrochemiluminescence radiation potential of the gold nanoclusters of the present invention is 0.57V, which is much lower than that of the traditional biruthenium pyridine / tripropylamine system (1.2V).

[0068] Comparative Example 1

[0069] The application is the same as described in Example 2, except that tert-butylamine-borane is replaced with tripropylamine, and the electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 7 ,from Figure 7 As can be seen, with tripropylamine as the co-reactant, the dual-ligand-stabilized gold nanoclusters emit weak electrochemiluminescence at a low radiation potential of 0.57V, and the maximum electrochemiluminescence radiation potential is much higher than that of tert-butylamine-borane as the co-reactant.

[0070] Comparative Example 2

[0071] The application is the same as described in Example 2, except that tert-butylamine-borane is replaced with triethylamine, and the electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 8 ,from Figure 8 It can be seen that with triethylamine as a co-reactant, the dual-ligand-stabilized gold nanoclusters emit weak electrochemiluminescence at a low radiation potential of 0.57V, and the maximum electrochemiluminescence radiation potential is much higher than that of tert-butylamine-borane as a co-reactant.

[0072] Comparative Example 3

[0073] The application is the same as described in Example 2, except that tert-butylamine-borane is replaced with 2-(dibutylamino)ethanol, and the electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 9 ,from Figure 9 As can be seen, with 2-(dibutylamino)ethanol as a co-reactant, the dual-ligand-stabilized gold nanoclusters emit weak electrochemiluminescence at a low radiation potential of 0.57V, and the maximum electrochemiluminescence radiation potential is much higher than that of tert-butylamine-borane as a co-reactant.

[0074] Comparative Example 4

[0075] The application is the same as described in Example 2, except that tert-butylamine-borane is replaced with triethanolamine, and the electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 10 ,from Figure 10 As can be seen, with triethanolamine as a co-reactant, the dual-ligand-stabilized gold nanoclusters emit weak electrochemiluminescence at a low radiation potential of 0.57V, and the maximum electrochemiluminescence radiation potential is much higher than that of tert-butylamine-borane as a co-reactant.

[0076] Example 5

[0077] The application is the same as described in Example 2, except that the co-reactant is removed, and the electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 11 ,from Figure 11 It can be seen that, in the absence of a co-reactant, the dual-ligand-stabilized gold nanoclusters emit weak electrochemiluminescence at a low radiation potential of 0.57V, and the maximum electrochemiluminescence radiation potential is much higher than that of tert-butylamine-borane as a co-reactant.

[0078] Comparative Example 6

[0079] Preparation of gold nanoclusters coated with thiomalic acid:

[0080] 625 μL of 96 mM H4AuCl4 solution was ultrasonically mixed with 20 mL of 9.6 mM thiomalic acid solution and added to a three-necked flask. The mixture was then heated under reflux at 95 °C for 144 h. After the reaction was complete, isopropanol was added, and the precipitate was collected by centrifugation at 13000 rpm to obtain thiomalic acid-coated gold nanoclusters.

[0081] Thiomalic acid-coated gold nanoclusters were prepared into a 2 mg / mL thiomalic acid-coated gold nanocluster solution.

[0082] A 10 μL solution of gold nanoclusters coated with thiomalic acid was dropped onto the surface of a glassy carbon electrode and dried at room temperature to obtain a gold nanocluster modified electrode. A three-electrode system was formed by using the gold nanocluster modified electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt wire as the counter electrode in a 0.1 mol / L phosphate buffer solution (pH 7.4) containing 10 mmol / L tert-butylamine-borane co-reactant.

[0083] The electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 12 ,from Figure 12 It can be seen that although thiomalic acid-stabilized gold nanoclusters can also exhibit low-potential electrochemiluminescence at 0.57 V, their electrochemiluminescence intensity is much lower than that of dual-ligand-stabilized gold nanoclusters. Figure 6 ).

[0084] Comparative Example 7

[0085] Preparation of sodium citrate-coated gold nanoclusters:

[0086] 625 μL of 96 mM H4AuCl4 solution was ultrasonically mixed with 20 mL of 0.15 mM sodium citrate solution and added to a three-necked flask. The mixture was then heated under reflux at 95 °C for 144 h. After the reaction was complete, isopropanol was added, and the precipitate was collected by centrifugation at 13000 rpm to obtain sodium citrate-coated gold nanoclusters.

[0087] Sodium citrate-coated gold nanoclusters were prepared into a 2 mg / mL sodium citrate-coated gold nanocluster solution;

[0088] A 10 μL solution of sodium citrate-coated gold nanoclusters was dropped onto the surface of a glassy carbon electrode and dried at room temperature to obtain a gold nanocluster modified electrode. A three-electrode system was formed using the gold nanocluster modified electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt wire as the counter electrode in a 0.1 mol / L phosphate buffer solution (pH 7.4) containing 10 mmol / L tert-butylamine-borane co-reactant.

[0089] The electrochemiluminescence intensity-(potential)-time curve obtained by cyclic voltammetry is shown below. Figure 13 ,from Figure 13 It can be seen that single-ligand stable gold nanoclusters (sodium citrate stable gold nanoclusters) cannot produce low-potential electrochemiluminescence radiation.

Claims

1. A near-infrared low-potential electrochemiluminescence dual-ligand stabilized gold nanoclusters, wherein the gold nanoclusters are co-coated with citrate and thiomalic acid dual ligands, and have a spherical morphology with a diameter of 1-5 nm. They are capable of generating low-potential electrochemiluminescence radiation in the near-infrared region in an aqueous system. The aqueous solution of the gold nanoclusters is brownish-yellow, with a strong absorption peak at 564 nm in the UV-Vis spectrum; the maximum fluorescence emission wavelength is 815 nm, and no obvious fluorescence is observed under UV light. The maximum wavelength of its electrochemiluminescence is 835 nm. The preparation method of the gold nanoclusters uses chloroauric acid as the gold source, and firstly, thiomalic acid is used as a reducing agent and stabilizer to reduce Au. 3+ A single-ligand-stabilized water-soluble gold nanoclusters were prepared. Then, the single-ligand-stabilized water-soluble gold nanoclusters were mixed with citrate and incubated together to obtain gold nanoclusters stabilized by thiomalic acid and sodium citrate.

2. The method for preparing near-infrared low-potential electrochemiluminescence dual-ligand-stabilized gold nanoclusters according to claim 1, comprising the following steps: (1) The chloroauric acid H4AuCl4 solution and the thiomalic acid ligand were ultrasonically mixed until homogeneous; (2) The solution obtained in step (1) is heated to react and a single-ligand stable water-soluble gold nanoclusters are obtained. The solution changes from colorless to brownish-yellow. (3) Add citrate to the solution prepared in step (2), mix by sonication, and incubate at room temperature; (4) After the reaction is complete, centrifuge to remove the large particles at the bottom, purify the solution with isopropanol, and the resulting precipitate is the gold nanocluster with dual ligands.

3. The method according to claim 2, characterized in that, In step (1), the molar ratio of gold to thiomalic acid in chloroauric acid is 1:(1-5).

4. The method according to claim 2, characterized in that, In step (1), the concentration of the H4AuCl4 solution is 80-100mM.

5. The method according to claim 2, characterized in that, In step (2), the heating temperature is 90-100℃ and the heating time is 130-150h.

6. The method according to claim 2, characterized in that, In step (3), the molar ratio of gold in citrate to chloroauric acid is 1:350-500.

7. The method according to claim 2, characterized in that, In step (3), the incubation time at room temperature is 0.5-3h. In step (4), isopropanol is purified by adding isopropanol to the solution and centrifuging at 13000-14000 rpm.

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