A fluorescent metal nanocluster and its preparation method and application

Abstract

The present invention discloses a fluorescent metal nanocluster, a preparation method, and an application thereof, belonging to the field of heavy metal detection technology. The fluorescent metal nanocluster comprises a nickel metal nanostructure and a cysteine ligand, wherein the cysteine ligand is attached to the nickel metal nanostructure via a chemical bond, and the fluorescent metal nanocluster has the optical property of aggregation-induced fluorescence enhancement. The preparation method is simple, easy to operate, low in cost, and green and mild. The fluorescent metal nanocluster can be quenched by copper ions, and therefore, it can identify copper ions rapidly, sensitively, and with high specificity. The fluorescent metal nanocluster can be used to detect heavy metal pollutants in samples such as water bodies, and has potential important application value in the field of environmental monitoring and protection.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metals, and in particular to a fluorescent metal nanocluster and a preparation method and application thereof. Background Art

[0002] Due to the rapid industrial development of modern life, heavy metal pollution has become a pressing concern worldwide. Copper ions are one of the most abundant essential metal elements in living systems. As a cofactor for numerous enzymes, they are crucial for redox homeostasis, intracellular metabolic balance, and gene expression. On the other hand, excessive copper ions may promote the formation of reactive oxygen species (ROS) and lead to cell death through copper apoptosis. Long-term exposure to high concentrations of copper ions may cause damage to the kidneys, liver, and gastrointestinal system. Furthermore, a range of diseases, including Alzheimer's disease, Menkes disease, and Parkinson's disease, are associated with disrupted copper ion homeostasis. Both copper ion deficiency and excess can adversely affect human physiological functions. Taking these factors into consideration, many international organizations, such as the U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO), have established limits for copper ions in water and food.

[0003] Currently, commonly used copper ion detection technologies include atomic absorption spectroscopy, X-ray absorption spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and inductively coupled plasma atomic emission spectrometry (ICP-AES). However, these methods still have some drawbacks, such as the need for expensive analytical instruments, complex pretreatment procedures, experienced technicians, and the inability to analyze biological samples and achieve rapid on-site detection.

[0004] Therefore, it is of great significance to develop sensitive and simple technologies that can quickly and effectively detect copper ions.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a fluorescent metal nanocluster and its preparation method and application to improve the above technical problems.

[0007] This application can be implemented as follows:

[0008] In a first aspect, the present application provides a fluorescent metal nanocluster comprising a nickel metal nanostructure and a cysteine ligand, wherein the cysteine ligand is attached to the nickel metal nanostructure via a chemical bond.

[0009] In an optional embodiment, the fluorescent metal nanoclusters have at least one of the following characteristics:

[0010] Feature 1: The particle size of fluorescent metal nanoclusters is 2 to 9 nm;

[0011] Feature 2: The maximum excitation wavelength of fluorescent metal nanoclusters is 400nm;

[0012] Feature 3: The maximum emission wavelength of fluorescent metal nanoclusters is 480nm.

[0013] In a second aspect, the present application provides a method for preparing fluorescent metal nanoclusters as described in the aforementioned embodiment, comprising the following steps: subjecting a nickel salt and cysteine to a hydrothermal reaction under solution conditions to form fluorescent metal nanoclusters;

[0014] In an optional embodiment, the molar ratio of nickel salt to cysteine is 1:1-3000.

[0015] In an alternative embodiment, the nickel salt includes at least one of nickel chloride, nickel sulfate, and nickel nitrate.

[0016] In an optional embodiment, the nickel salt aqueous solution and the cysteine aqueous solution are mixed and then subjected to a hydrothermal reaction.

[0017] In an optional embodiment, the concentration of the nickel salt aqueous solution is 10 to 1000 mmol / L, preferably 50 to 500 mmol / L, and more preferably 100 mmol / L.

[0018] In an optional embodiment, the concentration of the cysteine aqueous solution is 1 to 300 mmol / L, preferably 100 to 300 mmol / L, and more preferably 300 mmol / L.

[0019] In an optional embodiment, the cysteine aqueous solution further contains NaOH, and the molar ratio of NaOH to cysteine is 1:1 to 1.5; preferably, the molar ratio of NaOH to cysteine is 1:1.25.

[0020] In an optional embodiment, the temperature of the hydrothermal reaction is 50-100°C, and the time of the hydrothermal reaction is 3-72 hours; preferably, the temperature of the hydrothermal reaction is 85-95°C, and the time of the hydrothermal reaction is 24-48 hours; more preferably, the temperature of the hydrothermal reaction is 90°C, and the time of the hydrothermal reaction is 48 hours.

[0021] In a third aspect, the present application provides a fluorescent solution having the optical property of aggregation-induced fluorescence enhancement, which includes the fluorescent metal nanoclusters as described in the aforementioned embodiment and a solvent.

[0022] In an optional embodiment, the solvent includes water and a polar organic solvent.

[0023] In an optional embodiment, the solvent comprises at least one of ethylene glycol, methanol, ethanol and dimethylformamide; preferably, the solvent comprises ethylene glycol;

[0024] In an optional embodiment, the volume content of ethylene glycol in the solvent is ≥30%; preferably, the volume content of ethylene glycol in the solvent is ≥90%.

[0025] In a fourth aspect, the present application provides the use of fluorescent metal nanoclusters according to the aforementioned embodiments in detecting copper ions.

[0026] In an optional embodiment, the linear range of copper ion detection is 2 μmol / L to 800 μmol / L, and the detection limit is 1.03 μmol / L.

[0027] In a fifth aspect, the present application provides a method for detecting copper ions, comprising the following steps: using the fluorescent metal nanoclusters of the aforementioned embodiment as fluorescent probes to detect copper ions.

[0028] In an optional embodiment, the fluorescent metal nanoclusters are first mixed with the sample to be detected, and then the fluorescence detection is performed.

[0029] In an optional embodiment, the excitation wavelength used for fluorescence detection is 380-420 nm, preferably 415 nm.

[0030] The beneficial effects of this application include:

[0031] Fluorescent metal nanoclusters formed by chemically attaching cysteine ligands to nickel metal nanostructures exhibit the optical property of aggregation-induced fluorescence enhancement. Their preparation method is simple, easy to operate, low-cost, and green and gentle. These fluorescent metal nanoclusters can be used as fluorescent probes, quenched by the fluorescence of copper ions, enabling rapid, sensitive, and highly specific identification of copper ions. Using these fluorescent probes for copper ion detection overcomes the shortcomings of existing copper ion detection methods, which are time-consuming, complex, and costly. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 (A) is the UV-visible absorption spectrum of Cys-Ni NCs in Example 1; Figure 1 (B) is the fluorescence excitation spectrum and fluorescence emission spectrum of Cys-Ni NCs in Example 1;

[0034] Figure 2 is the infrared spectrum of Cys-Ni NCs in Example 1;

[0035] Figure 3 TEM image of Cys-Ni NCs in Example 1;

[0036] Figure 4 Figure 1 is the fluorescence emission spectra of Cys-Ni NCs with aggregation-induced enhancement effect in different proportions of ethylene glycol in Experimental Example 1;

[0037] Figure 5 This is the linear relationship diagram of Cys-Ni NCs used in the detection of copper ions in Experimental Example 2;

[0038] Figure 6 This is the selective experimental result of Cys-Ni NCs used in the detection of copper ions in Experimental Example 3. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0040] The fluorescent metal nanoclusters provided in this application and their preparation methods and applications are described in detail below.

[0041] The fluorescent metal nanoclusters proposed in the present application can be represented by Cys-Ni NCs, which include nickel metal nanostructures and cysteine ligands, and the cysteine ligands are attached to the nickel metal nanostructures through chemical bonds.

[0042] The particle size of the fluorescent metal nanoclusters is 2 to 9 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm or 9 nm, and the average particle size is about 4.5 nm.

[0043] If the particle size of the fluorescent metal nanoclusters is less than 2 nm, it is not conducive to the formation of stable clusters; if the particle size of the fluorescent metal nanoclusters is greater than 9 nm, it is not conducive to the uniform dispersion of the clusters in the solution.

[0044] In the present application, the maximum excitation wavelength of the fluorescent metal nanoclusters is 400 nm, the maximum emission wavelength is 480 nm, and they have the optical property of aggregation-induced fluorescence enhancement.

[0045] The fluorescent metal nanoclusters formed by the above-mentioned cysteine ligands attached to the nickel metal nanostructures through S-Ni chemical bonds can be used as fluorescent probes to quickly, sensitively and highly specifically identify copper ions, overcoming the shortcomings of existing copper ion detection such as long time consumption, cumbersome steps and high cost.

[0046] Accordingly, the present application also provides a method for preparing the above-mentioned fluorescent metal nanoclusters, which may include the following steps: subjecting nickel salt and cysteine to a hydrothermal reaction under solution conditions to form fluorescent metal nanoclusters.

[0047] For reference, the nickel salt includes at least one of nickel chloride, nickel sulfate, and nickel nitrate. Other nickel salts are also possible, which are not listed here. The molar ratio of the nickel salt to cysteine can be 1:1 to 3000, such as 1:1, 1:5, 1:10, 1:50, 1:100, 1:200, 1:500, 1:1000, 1:1500, 1:2000, 1:2500, or 1:3000.

[0048] In the above process, nickel salt is used as raw material, and cysteine is used as stabilizer and reducing agent, and fluorescent metal nanoclusters can be synthesized through a one-pot method.

[0049] In some embodiments, the nickel salt aqueous solution and the cysteine aqueous solution may be mixed and then subjected to a hydrothermal reaction.

[0050] The concentration of the nickel salt aqueous solution can be 10 to 1000 mmol / L, such as 10 mmol / L, 20 mmol / L, 50 mmol / L, 100 mmol / L, 200 mmol / L, 500 mmol / L, 800 mmol / L, or 1000 mmol / L, or any other value within the range of 10 to 1000 mmol / L. In some preferred embodiments, the concentration of the nickel salt aqueous solution is 50 to 500 mmol / L. In some more preferred embodiments, the concentration of the nickel salt aqueous solution is 100 mmol / L. In a more preferred embodiment, the fluorescence intensity of the metal nanoclusters obtained in the experiment is the highest.

[0051] The concentration of the cysteine aqueous solution can be 1 to 300 mmol / L, such as 1 mmol / L, 5 mmol / L, 10 mmol / L, 50 mmol / L, 100 mmol / L, 150 mmol / L, 200 mmol / L, 250 mmol / L, or 300 mmol / L, or any other value within the range of 1 to 300 mmol / L. In some preferred embodiments, the concentration of the cysteine aqueous solution is 100 to 300 mmol / L. In some more preferred embodiments, the concentration of the cysteine aqueous solution is 300 mmol / L.

[0052] In the present application, the aqueous cysteine solution further contains NaOH to completely dissolve the cysteine in water. The molar ratio of NaOH to cysteine can be 1:1 to 1.5, such as 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, or any other value within the range of 1:1 to 1.5. In some preferred embodiments, the molar ratio of NaOH to cysteine is 1:1.25.

[0053] In the present application, the temperature of the hydrothermal reaction can be 50-100°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, or any other value within the range of 50-100°C. In some preferred embodiments, the temperature of the hydrothermal reaction is 85-95°C. In some more preferred embodiments, the temperature of the hydrothermal reaction is 90°C.

[0054] The hydrothermal reaction time can be 3 to 72 hours, such as 3 hours, 5 hours, 10 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, 48 hours, 54 hours, 60 hours, 66 hours or 72 hours, or any other value within the range of 3 to 72 hours. In some preferred embodiments, the hydrothermal reaction time is 24 to 48 hours. In some more preferred embodiments, the hydrothermal reaction time is 48 hours.

[0055] In some embodiments, fluorescent metal nanoclusters can be prepared as follows:

[0056] S1. Prepare 0.05-1 mL of NiCl2 aqueous solution with a concentration of 10-1000 mmol / L.

[0057] S2. Prepare 5-100 mL of a mixed aqueous solution of cysteine with a concentration of 1-300 mmol / L and 1-450 mmol / L NaOH.

[0058] S3. Add NiCl2 solution to the mixed aqueous solution of cysteine and NaOH so that the molar ratio of NiCl2 to cysteine is 1:1 to 1:3000, and mix thoroughly.

[0059] S4. The mixed solution is subjected to a hydrothermal reaction in a water bath at 50-100° C.; the hydrothermal reaction time is 3-72 hours.

[0060] It should be noted that the mixed solution obtained after the hydrothermal reaction can be used directly for detection, or it can be freeze-dried and then refrigerated until needed. Refrigeration can effectively prevent the deterioration of the fluorescent probe, extend the probe's service life, and ensure the accuracy of the detection results. The refrigeration temperature is 4°C.

[0061] In addition, the present application also provides a fluorescent solution having the optical property of aggregation-induced fluorescence enhancement, which includes a solvent and the above-mentioned fluorescent metal nanoclusters.

[0062] The solvent includes water and a polar organic solvent, for example, at least one of ethylene glycol, methanol, ethanol and dimethylformamide. In some preferred embodiments, the solvent includes ethylene glycol.

[0063] In the fluorescent solution, the higher the ethylene glycol content, the stronger the fluorescence intensity. Therefore, the fluorescent metal nanoclusters have an aggregation-induced fluorescence enhancement phenomenon in a mixed solution of ethylene glycol and water.

[0064] Preferably, the volume content of ethylene glycol in the solvent is ≥30%, such as 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95%, etc. More preferably, the volume content of ethylene glycol in the solvent is ≥90% (excluding 100%) to obtain better fluorescence imaging effect.

[0065] Furthermore, the present application also provides the use of the above-mentioned fluorescent metal nanoclusters in detecting copper ions.

[0066] The inventors have creatively discovered that copper ions can quench the fluorescence of the fluorescent metal nanoclusters described in this application. By performing concentration gradient detection of copper ions, they found that cysteine-protected nickel nanoclusters exhibit specific selectivity and high sensitivity for copper ions. The linear range for copper ion detection is 2 μmol / L to 800 μmol / L, with a detection limit of 1.03 μmol / L.

[0067] Correspondingly, the present application also provides a method for detecting copper ions, which comprises the following steps: using the above-mentioned fluorescent metal nanoclusters as fluorescent probes to detect copper ions.

[0068] As a reference, the fluorescent probe can be mixed with the sample to be detected, and then fluorescence detection can be performed.

[0069] The excitation wavelength used for fluorescence detection can be 380-420 nm, preferably 415 nm. Under conditions of an excitation wavelength of 415 nm, the peak height of the emission light of the test solution at 490 nm is preferably determined using a 1 mL detection standard. In the fluorescent metal nanocluster system, 100 μL of Cys-Ni NCs is added to the test solution, and the volume is then made up to 1 mL with water.

[0070] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0071] Chemicals and Reagents: Nickel(II) chloride hexahydrate (NiCl2·6H2O), L-cysteine, copper(II) nitrate trihydrate (Cu(NO3)2·3H2O), and ethylene glycol (EG) were purchased from Aladdin Reagent Co. Ltd. (Shanghai, China). All chemicals were of at least analytical grade and used without further purification. Double-distilled water was used in the experiments.

[0072] Example 1

[0073] This embodiment provides a fluorescent metal nanocluster, which is prepared by the following method:

[0074] Add 0.1 mL of a 100 mmol / L NiCl2 aqueous solution to a 10 mL solution of a 300 mmol / L cysteine and 400 mmol / L NaOH solution and mix thoroughly. Heat and stir at 90°C for 48 hours to produce a dark brown nickel nanocluster aqueous solution. Store the final product in a refrigerator at 4°C until ready for use.

[0075] Structural characterization of Cys-Ni NCs:

[0076] The UV-visible absorption spectrum, fluorescence excitation spectrum and fluorescence emission spectrum of Cys-Ni NCs prepared in this example are shown in the figure below. Figure 1 As shown by Figure 1 The Cys-Ni NCs prepared in this example exhibit a distinct shoulder peak, while the raw material cysteine lacks a distinct UV absorption peak, demonstrating that the Cys-Ni NCs prepared in this example and cysteine are not the same substance. Furthermore, the nanoclusters exhibit a maximum excitation wavelength of 400 nm and a maximum emission wavelength of 480 nm.

[0077] In order to further study the chemical structure of Cys-Ni NCs, the infrared spectra (FT-IR) of the nanoclusters and their raw material cysteine were measured and compared. Figure 2 As shown, the most significant difference between the two spectra is the cysteine peak at 2551 cm -1 The characteristic peak of -SH stretching vibration at 100 nm disappeared in Cys-Ni NCs. This phenomenon indicates that during the formation of nickel nanoclusters, the SH bond of cysteine breaks and the cysteine ligand attaches to the nickel metal nanostructure through S-Ni chemical bonds, forming Cys-Ni NCs.

[0078] Furthermore, the Cys-Ni NCs of this embodiment were observed by transmission electron microscopy. Figure 3 As shown, it appears as spherical particles with a diameter of about 4.5 nm.

[0079] Example 2

[0080] This embodiment provides a fluorescent metal nanocluster, which is prepared by the following method:

[0081] Add 0.1 mL of a 10 mmol / L NiCl2 aqueous solution to a 10 mL solution of a 300 mmol / L cysteine and 400 mmol / L NaOH solution and mix thoroughly. Heat and stir at 90°C for 24 hours to produce a light brown nickel nanocluster aqueous solution. Store the final product in a refrigerator at 4°C until ready for use.

[0082] Example 3

[0083] This embodiment provides a fluorescent metal nanocluster, which is prepared by the following method:

[0084] Add 0.1 mL of a 100 mmol / L NiCl₂ aqueous solution to a 10 mL solution of 100 mmol / L cysteine and 150 mmol / L NaOH (150 mmol / L) and mix thoroughly. Heat and stir at 90°C for 24 hours to produce a dark brown nickel nanocluster aqueous solution. Store the final product in a refrigerator at 4°C until ready for use.

[0085] Example 4

[0086] This embodiment provides a fluorescent metal nanocluster, which is prepared by the following method:

[0087] Add 0.2 mL of a 100 mmol / L NiCl₂ aqueous solution to a 20 mL solution of a 300 mmol / L cysteine and 400 mmol / L NaOH solution and mix thoroughly. Heat and stir at 90°C for 48 hours to produce a dark brown nickel nanocluster aqueous solution. Store the final product in a refrigerator at 4°C until ready for use.

[0088] Example 5

[0089] This embodiment provides a fluorescent metal nanocluster, which is prepared by the following method:

[0090] Add 0.1 mL of a 100 mmol / L NiCl₂ aqueous solution to a 10 mL solution of a 5 mmol / L cysteine and 7.5 mmol / L NaOH solution and mix thoroughly. Heat and stir at 90°C for 5 hours to obtain a light yellow nickel nanocluster aqueous solution. Store the final product in a refrigerator at 4°C until ready for use.

[0091] Example 6

[0092] This embodiment provides a fluorescent metal nanocluster, which is prepared by the following method:

[0093] Add 0.1 mL of a 100 mmol / L NiCl₂ aqueous solution to a 10 mL solution of a 300 mmol / L cysteine and 400 mmol / L NaOH solution and mix thoroughly. Heat and stir at 50°C for 24 hours to produce a light yellow nickel nanocluster aqueous solution. Store the final product in a refrigerator at 4°C until ready for use.

[0094] Test Example 1

[0095] The same amount of Cys-Ni NCs prepared in Example 1 was dissolved in different ratios of ethylene glycol / water solution (ethylene glycol / water were 0%, 10%, 30%, 50%, 70%, 90%). Under the excitation of 400nm wavelength light, the fluorescence spectrum of Cys-Ni NCs was tested, and the emission peak fluorescence intensity at 480nm wavelength was detected. The results are shown in Figure 2. Figure 4 As shown in Figure 3, the fluorescence intensity of Cys-Ni NCs increases with the increase of ethylene glycol ratio, indicating that Cys-Ni NCs have solvent-induced aggregation-induced fluorescence enhancement (AIEE).

[0096] Test Example 2

[0097] 100 μL of copper ion aqueous solution of different concentrations was added to 800 μL of pure water and thoroughly mixed in a 1.5 mL centrifuge tube. Before measuring the fluorescence spectrum, 100 μL of the Cys-Ni NCs concentrated solution (0.1 mmol / L) prepared in Example 1 was added to the detection system. The effects of different concentrations of copper ions on the fluorescence signal of the Cys-Ni NCs probe were measured (final concentrations were 0, 2, 10, 25, 50, 100, 200, 300, 400, 500, and 800 μmol / L). Under excitation with 415 nm wavelength light, the fluorescence spectrum of Cys-Ni NCs was measured, and the emission peak fluorescence intensity at a wavelength of 490 nm was measured. The fluorescence signal of the added copper ions was measured, and the fluorescence intensity at the maximum emission peak position was recorded as I, and the fluorescence intensity of the Cys-Ni NCs probe itself was recorded as I0. The experiment was repeated three times, and the results were averaged.

[0098] The response of Cys-Ni NCs to different concentrations of copper ions was studied by fluorescence emission spectroscopy. Figure 5 As shown in the figure, the fluorescence quenching degree of Cys-Ni NCs increases with the increase of copper ions, and the relative fluorescence intensity linear detection curve can be expressed as I0 / I=0.00579[Cu 2+ ]+0.9961, correlation coefficient R 2=0.9912, and the constructed linear range for copper ion detection was 2-800 μmol / L. The detection limit was 1.03 μmol / L, far below the WHO and EPA limits for copper ion. These results demonstrate that the Cys-Ni NCs nickel nanocluster fluorescent probe prepared according to the present invention has the potential to be used for analyzing and detecting copper ion content in real samples.

[0099] Test Example 3

[0100] Selectivity is an important indicator for establishing analytical methods for environmental pollutants. To evaluate the specificity of this probe for copper ions and potential competitors, various metal ions were tested under the same conditions, including Hg, which is strictly restricted in the Chinese Pharmacopoeia. 2+ , Pb 2+ and Cd 2+ and Na, which is commonly found in environmental samples + , K + 、Al 3+ Cr 3+ 、Ag + 、Sn 4+ , Ca 2+ 、Ba 2+ 、Sr 2 + and Zn 2+ The responses of Cys-Ni NCs to the above substances were evaluated by fluorescence assay. All ions were tested at a concentration of 100 μmol / L. 2+ It can cause a slight fluorescence enhancement, and the surfactant CTAB can avoid the Cd 2+ The fluorescence enhancement phenomenon caused by Cd 2+ This group of samples was spiked with CTAB. Figure 6 It can be seen that only Cu 2+ The fluorescence intensity decreased significantly, while other metal ions had no significant effect on the fluorescence intensity of the probe. The above results indicate that this method has good selectivity and can be applied to the detection of copper ions in environmental samples.

[0101] Test Example 4

[0102] In order to further verify the feasibility of this Cys-Ni NCs-based probe in practical applications, tap water and lake water were used as matrices for actual sample detection. 2+ The recovery rate was studied by testing using the method in Experimental Example 2. The Cys-Ni NCs were prepared as described in Example 1.

[0103] 1. Sample source

[0104] Tap water was collected from the laboratory of the University of Macau, and lake water was collected from the campus of the University of Macau.

[0105] 2. Testing process

[0106] All water samples were filtered through a 0.22 mm membrane prior to testing. Before fluorescence emission spectroscopy, 100 μL of Cys-Ni NCs (0.1 mmol / L) was added to the sample. The detection volume was 1 mL, and the detection method was similar to that of Experimental Example 2. The test results were applied to the standard curve generated in Experimental Example 2.

[0107] The treated water samples were tested three times using the same method described above. No copper ions were detected in either sample.

[0108] 3. Detection spike recovery rate:

[0109] 25 μmol / L, 200 μmol / L and 500 μmol / L copper ion standards were added to the samples respectively, and the recovery rate of the spiked copper ions of the above two water samples was detected. The detection method was based on Test Example 2. The test results were substituted into the standard curve drawn in Test Example 2 for calculation and determination of the recovery rate. The test results are shown in Table 1.

[0110] Table 1 Recovery results of copper ions in tap water and lake water samples

[0111]

[0112] The method achieved recoveries ranging from 93% to 101% for tap water and 88% to 98% for lake water samples. Detailed information is provided in Table 1. These results demonstrate that this probe is a highly reliable and easy-to-use method for the detection of copper ions in real samples.

[0113] In summary, the present application successfully prepared a new type of fluorescent metal nanoclusters (Cys-Ni NCs) by reacting cysteine with nickel salts, and the preparation method is simple, easy to operate, low in cost, green and mild, and suitable for mass production. Secondly, the fluorescent metal nanoclusters are highly stable, have the property of aggregation-induced fluorescence enhancement, and do not require any modification steps for the material. Thirdly, the interaction between copper ions and the functional groups on the surface of Cys-Ni NCs can be utilized to produce the fluorescence quenching phenomenon of nickel nanoclusters, which can be used as a fluorescent probe for the detection of copper ions. Finally, the method proposed in the present application has good selectivity, high sensitivity, wide detection range, simple operation, can be widely used in actual sample detection, and is also of great significance for the monitoring of heavy metals in environmental samples.

[0114] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. Application of fluorescent metal nanoclusters in the detection of copper ions; The fluorescent metal nanocluster comprises a nickel metal nanostructure and a cysteine ligand, wherein the cysteine ligand is attached to the nickel metal nanostructure via a chemical bond; The particle size of the fluorescent metal nanocluster is 2 to 9 nm; the maximum excitation wavelength of the fluorescent metal nanocluster is 400 nm; the maximum emission wavelength of the fluorescent metal nanocluster is 480 nm; The preparation of the fluorescent metal nanoclusters comprises the following steps: A nickel salt aqueous solution and a cysteine aqueous solution are mixed and then subjected to a hydrothermal reaction to form the fluorescent metal nanoclusters; the molar ratio of the nickel salt to the cysteine is 1:1 to 3000; the nickel salt comprises at least one of nickel chloride, nickel sulfate, and nickel nitrate; the concentration of the nickel salt aqueous solution is 50 to 500 mmol / L; the concentration of the cysteine aqueous solution is 100 to 300 mmol / L; the cysteine aqueous solution further contains NaOH, and the molar ratio of NaOH to cysteine is 1:1 to 1.5; The temperature of the hydrothermal reaction is 85 to 95° C., and the time of the hydrothermal reaction is 24 to 48 hours; The linear range of copper ion detection is 2μmol / L~800μmol / L, and the detection limit is 1.03μmol / L.

2. The use according to claim 1, characterized in that The concentration of the nickel salt aqueous solution is 100 mmol / L.

3. The use according to claim 1, characterized in that The concentration of the cysteine aqueous solution is 300 mmol / L.

4. The use according to claim 1, characterized in that The temperature of the hydrothermal reaction is 90° C., and the time of the hydrothermal reaction is 48 h.

5. A method for detecting copper ions, characterized in that, The method comprises the following steps: using the fluorescent metal nanoclusters used in any one of claims 1 to 4 as fluorescent probes to detect copper ions.

6. The detection method according to claim 5, characterized in that The fluorescent metal nanoclusters are first mixed with a sample to be detected, and then fluorescence detection is performed.

7. The detection method according to claim 6, characterized in that The excitation wavelength used for fluorescence detection was 380-420 nm.

8. The detection method according to claim 7, characterized in that The excitation wavelength used for fluorescence detection was 415 nm.

9. Use of a fluorescent solution in detecting copper ions, wherein the fluorescent solution has the optical property of aggregation-induced fluorescence enhancement, characterized in that: The invention comprises the fluorescent metal nanoclusters used in any one of claims 1 to 4 and a solvent.

10. The use according to claim 9, characterized in that The solvent includes water and a polar organic solvent.

11. The use according to claim 10, characterized in that The solvent includes at least one of ethylene glycol, methanol, ethanol and dimethylformamide.

12. The use according to claim 11, characterized in that The solvent includes ethylene glycol.

13. The use according to claim 11 or 12, characterized in that The volume content of ethylene glycol in the solvent is ≥30%.

14. The use according to claim 13, characterized in that The volume content of ethylene glycol in the solvent is ≥90%.

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