Double-ligand rare earth fluorescent nanoparticles for sensitively detecting copper ions

Abstract

The invention discloses a double-ligand rare earth fluorescent nanoparticle for sensitively detecting copper ions, the double-ligand rare earth fluorescent nanoparticle is a lanthanide element-based ratio type fluorescent nanoparticle for detecting Cu < 2 + >, and the fluorescent nanoparticle has double emission sites, the fluorescent nano particles show strong blue and red fluorescence at the positions of 423 nm and 618 nm; the preparation method of the double-ligand rare earth fluorescent nanoparticles comprises the following steps: preparing a europium nitrate solution, adding a DMSO solution containing luminol into the europium nitrate solution, then adding a PBS buffer solution into the europium nitrate solution, and stirring at room temperature to obtain a clear and transparent solution containing a precursor Eu-lu complex; the preparation method of the double-ligand rare earth fluorescent nanoparticles is simple, the copper ions can be stably measured for a long time, the stability is good, the preservation time is long, and the double-ligand rare earth fluorescent nanoparticles play an important role in high-sensitivity and visual detection of the copper ions.

Description

Technical Field

[0001] The invention relates to the technical field of copper ion detection, and in particular to a dual-ligand rare earth fluorescent nanoparticle for sensitively detecting copper ions. Background Art

[0002] Copper (Cu) is a heavy metal and an environmental pollutant. Due to the toxicity of copper ions and their ability to aggregate in organisms, they can pollute water bodies and cause serious harm to human physical and mental health. Copper ions are essential trace elements for the human body. When the copper ion content exceeds the human body's needs, it will affect human body functions, leading to a series of diseases, including vomiting, diarrhea, Menkes syndrome, Wilson disease and other diseases. According to the national standard GB / T 7473-87, when the copper content in water reaches 0.01 mg / L, it has a significant inhibitory effect on the self-purification of the water body; when it exceeds 3.0 mg / L, it will produce odor; when it exceeds 15 mg / L, it will be undrinkable. If copper-containing wastewater is used to irrigate farmland, copper will accumulate in the soil and crops, causing poor growth of crops, especially rice and barley, and contaminating grains. Therefore, the detection of copper ions in real water environments is of great significance.

[0003] So far, the main methods reported for detecting copper ions include inductively coupled plasma mass spectrometry (GC-MS), high performance liquid chromatography (HPLC), ultraviolet visible spectrophotometry, fluorescent probe method, and atomic absorption spectrometry. The above methods have been reported to detect copper ions in water environments and soil. However, current detection methods often have the disadvantages of requiring complex pretreatment, expensive detection instruments, inability to detect on-site in a timely manner, and the need for professional detection personnel. In contrast, the fluorescence method has attracted widespread attention because it does not require complex operations, has a short response time, low detection cost, and high sensitivity. Currently reported fluorescent probes for detecting copper ions mainly include carbon quantum dots, fluorescent nanoparticles, metal organic frameworks, etc. However, these fluorescent probes often have the disadvantages of complex synthesis, difficult to obtain raw materials, and short material life, which limit the practical application of traditional fluorescent probes.

[0004] Compared with traditional fluorescent materials, the advantages of lanthanide complex fluorescence include millisecond-level luminescence lifetime and fast fluorescence response speed; narrow emission peak (half-peak width is about 10nm) and can simultaneously present multi-color fluorescence; large Stokes shift, high sensitivity, and reduced background interference; the complex is stable and easy to store. Compared with organic emitting groups that rely on covalent bond breaking to produce fluorescence changes under stimulation, lanthanide coordination is more dynamic, so lanthanide complexes are more sensitive to fluorescence changes under stimulation. Therefore, lanthanide complex fluorescence detection has attracted more and more attention. Among them, europium ions are widely adopted in the preparation of lanthanide fluorescent nanoparticles because of their excellent performance, stable wavelength emission, and easy access. However, due to the participation of water molecules in the coordination of europium ions in the solvent, the characteristic emission of europium is easily quenched by water molecules and the fluorescence lifetime is also reduced, which limits the application of Eu fluorescent nanoparticles in water environments. Dual-ligand nanoparticles can hinder the coordination of water molecules in europium ion nanoparticles through saturated coordination with lanthanide ions, avoiding energy loss caused by water. Moreover, most lanthanide fluorescent probes rely on fluorescence changes at a single wavelength to detect substances, which is likely to be affected by the test environment and instrument changes, resulting in inaccurate qualitative analysis of the substance being measured. Dual-ligand nanoparticles can emit light at two wavelengths, and by recording the fluorescence intensity ratio of the two emission wavelengths, the impact of instrument fluctuations on content determination is minimized. Multiple fluorescence emissions also provide conditions for visual detection. Dual-ligand nanoparticle ratiometric fluorescence sensing can eliminate background interference and plays an important role in high-sensitivity and visual detection of copper ions.

[0005] Therefore, the present invention provides a dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions. The prepared dual-ligand fluorescent nanoparticle has dual emission wavelengths and can selectively and quantitatively detect copper ions through changes in the internal fluorescence intensity ratio between ligands, showing high selectivity and sensitivity. Summary of the invention

[0006] The purpose of the present invention is to provide a dual-ligand rare earth fluorescent nanoparticle for sensitively detecting copper ions. The prepared dual-ligand fluorescent nanoparticle has dual emission wavelengths and can selectively and quantitatively detect copper ions through changes in the internal fluorescence intensity ratio between ligands, showing high selectivity and sensitivity.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A dual-ligand rare earth fluorescent nanoparticle for sensitively detecting copper ions, wherein the dual-ligand rare earth fluorescent nanoparticle (Eu-lu-DPA) is used to detect Cu 2+ A lanthanide-based ratiometric fluorescent probe having dual emission sites, wherein the fluorescent probe exhibits strong blue and red fluorescence at 423 nm and 618 nm;

[0009] The preparation method of the dual-ligand rare earth fluorescent nanoparticles comprises the following steps:

[0010] (1) dissolving solid europium nitrate in ultrapure water to prepare a europium nitrate solution, adding a DMSO solution containing luminol to the europium nitrate solution, and then adding a PBS buffer solution thereto to obtain a mixture, and stirring the mixture at room temperature for 2 to 3 hours to obtain a clear and transparent solution containing a precursor Eu-Lu complex;

[0011] (2) Adding a pyridine dicarboxylic acid aqueous solution to the clear transparent solution containing the precursor Eu-lu complex and continuing to stir at room temperature for 2 to 3 hours to obtain a clear solution of the Eu-lu-DPA biligand complex, and storing it at 4° C. before use.

[0012] Preferably, the molar ratio of europium ions, luminol and dipicolinic acid in the clear solution of the Eu-lu-DPA biligand complex is 1.4:1:1.2.

[0013] Preferably, the pH value of the PBS buffer needs to be adjusted to 8 using sodium hydroxide.

[0014] The present application also claims to protect the application of a dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions, and the application of the dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions in the selective detection of copper ions in a water environment.

[0015] Preferably, the method for detecting copper ions is: adding 140 μM / L Eu-lu-DPA to solutions with different copper ion concentrations, after sufficient shaking, collecting the fluorescence spectrum with an excitation wavelength of 270 nm, and obtaining a fluorescence spectrum change graph of the dual-ligand rare earth fluorescent nanoparticles. The copper ions in the water environment can be quickly and quantitatively detected through the linear relationship of the fluorescence spectrum change graph.

[0016] Preferably, the fluorescence spectrum change diagram of the dual-ligand rare earth fluorescent nanoparticles takes the copper ion concentration as the abscissa and the fluorescence intensity ratio I as the ordinate. 618 / I 423 A linear relationship diagram is drawn with the relative decrease value of the fluorescence intensity ratio as the ordinate, and each relative decrease value of the fluorescence intensity ratio corresponds to a copper ion concentration. The copper ions in the water environment can be quickly and quantitatively detected through the linear relationship.

[0017] Specifically, the dual-ligand rare earth fluorescent nanoparticles have good dispersibility in water, stable fluorescent properties, dual emission sites, can be binary decoded through the intensity ratio of two different internal fluorescences, and are used to selectively detect copper ions in water environments; the specific detection method is as follows: anhydrous copper sulfate solid is dissolved in deionized water to prepare solutions containing copper ions of different concentrations (0-40 μM / L); copper ions of known different ion concentrations are added to the Eu-lu-DPA solution, and after sufficient shaking, the corresponding emission spectra are measured with an excitation wavelength of 270 nm to obtain characteristic emission spectra under different copper ion concentrations, and the copper ion concentration is used as the horizontal coordinate and the fluorescence ratio I is used as the horizontal coordinate. 618 / I 423 The relative reduction value is used as the ordinate to draw a two-dimensional decoding diagram. Each corresponding fluorescence intensity ratio corresponds to a decoding position. The corresponding copper ion concentration can be effectively sensed through the two-dimensional linear relationship diagram; this dual-ligand fluorescent nanoparticle can effectively avoid the uncontrollable errors caused by instrument detection; among them, I 423 ,I 618 Represent the fluorescence intensity at 423nm and 618nm respectively.

[0018] In the above technical solution, the dual-ligand rare earth fluorescent nanoparticles have dual emission sites, wherein the emission site of the rare earth europium ion is at 618nm, and the emission site of the ligand luminol is at 423nm. A relationship diagram can be made through the ratio of the two internal fluorescence intensities and applied to the qualitative and quantitative detection of copper ions.

[0019] In the above technical scheme, the ligand luminol in the dual-ligand rare earth fluorescent nanoparticles is a luminescent reagent containing aromatic groups, rich in a large number of electron-rich groups, has excellent biocompatibility and water solubility, and is usually used for electrochemical analysis and material luminescence detection; and luminol is non-toxic, inexpensive, and easy to obtain, and can act as a ligand for lanthanide ions.

[0020] Working mechanism of the present invention:

[0021] The synthesized Eu-lu-DPA exhibits the characteristic blue emission of luminol and the red emission of Eu under a single excitation wavelength, which are located at 423nm and 618nm respectively; the 618nm characteristic luminescence of Eu-DPA will be selectively quenched by copper ions. This is because the complexation of copper ions with the carboxylic acid groups involved in the coordination in Eu(DPA)3 causes the energy to be transferred from pyridinedicarboxylic acid to copper ions through the O-Cu-O bond, weakening the energy transferred to europium ions and weakening the 618nm red fluorescence. The self-assembly of luminol and europium ions is due to the aggregation-induced emission (AIE) effect and will not be affected by copper ions.

[0022] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0023] 1. The preparation method of the dual-ligand rare earth fluorescent nanoparticles of the present invention is simple, the raw materials are easily available, the water environment does not need to be pre-treated in advance, the operation is simple, and it can be used by inexperienced people;

[0024] 2. The dual-ligand rare earth fluorescent nanoparticles prepared by the present invention can stably measure copper ions for a long time, have good stability and long storage time, and europium ions have the advantages of millisecond-level luminescence lifetime, fast fluorescence response speed, narrow emission peak and large Stokes shift;

[0025] 3. The dual-ligand rare earth fluorescent nanoparticles prepared by the present invention can be quantitatively measured within a certain concentration range through the relationship between the copper ion concentration and the corresponding fluorescence intensity ratio, and have high sensitivity and selectivity to copper ions;

[0026] 4. Compared with traditional fluorescent nanoparticles emitting at a single wavelength, the dual-ligand rare earth fluorescent nanoparticles prepared by the present invention can emit light of two wavelengths with only a single excitation wavelength. By recording the fluorescence intensity ratio of the two emission wavelengths, the influence of instrument fluctuations on content determination is minimized. Multiple fluorescence emissions also provide conditions for visual detection. The ratiometric fluorescence sensing of the dual-ligand rare earth fluorescent nanoparticles can eliminate background interference, which plays an important role in high sensitivity and visual detection of copper ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, some of the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be made based on these drawings without paying any creative work.

[0028] Figure 1 is a SEM image of Eu-lu-DPA of Example 1 of the present invention;

[0029] Figure 2 is the XPS graph of Eu-lu-DPA of Example 1 of the present invention;

[0030] Figure 3 1 is the excitation spectrum and emission spectrum of the precursors Eu-lu and Eu-DPA of Eu-lu-DPA in Example 1 of the present invention;

[0031] Figure 4 is a fluorescence emission spectrum of Eu-lu-DPA of Example 1 of the present invention at different excitation wavelengths;

[0032] Figure 5This is a fluorescence stability effect diagram of Eu-lu-DPA in Example 1 of the present invention at different days;

[0033] Figure 6 This is a fluorescence spectrum obtained after Eu-lu-DPA in Example 1 of the present invention detects aqueous solutions with different copper ion concentrations;

[0034] Figure 7 is a curve diagram showing the relationship between the relative fluorescence ratio of Eu-lu-DPA and the copper ion concentration in Example 1 of the present invention;

[0035] Figure 8 This is a spectrum diagram of Eu-lu-DPA in Example 1 of the present invention accurately detecting copper ions in common influencing substances. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, a specific implementation scheme is now described in detail.

[0037] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to the different requirements of specific use, and the implementation conditions not indicated are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0038] Example 1

[0039] See attached Figure 1-8 This embodiment provides a dual-ligand rare earth fluorescent nanoparticle for sensitively detecting copper ions. The preparation method of the dual-ligand rare earth fluorescent nanoparticle comprises the following steps:

[0040] (1) dissolving solid europium nitrate in ultrapure water to prepare a europium nitrate solution, adding 1.4 mL of anhydrous europium nitrate (0.473 mg, 1 mM) aqueous solution to a 50 mL centrifuge tube containing 80 μL of luminol (0.142 mg, 0.01 M) DMSO solution, and then adding 8.45 mL of PBS buffer (0.01 M) adjusted to pH = 8 with 1 M sodium hydroxide to obtain a mixture, and stirring the mixture at room temperature for 2 h to obtain a clear and transparent solution of Eu-Lu complex;

[0041] (2) Add 70uL of pyridinedicarboxylic acid (0.234mg, 0.02M) aqueous solution to the clear transparent solution containing the precursor Eu-lu complex and continue stirring at room temperature for 2h to obtain a clear solution of the Eu-lu-DPA biligand complex, and store it at 4°C before use for subsequent use.

[0042] Product Characterization:

[0043] Attached Figure 1 The morphology and microstructure of the Eu-lu-DPA complex synthesized in Example 1 are characterized by scanning electron microscopy (SEM); the Eu-lu-DPA dual ligand complex has a regular size, is flaky, has a smooth surface, and forms a new nano-flaky structure. This may be due to the addition of DPA as a ligand to coordinate with the metal, which affects the original structure of the precursor Eu-lu complex, or the addition of DPA may affect the microenvironment;

[0044] Attached Figure 2 The elemental composition of the Eu-lu-DPA complex synthesized in Example 1 was identified by X-ray photoelectron spectroscopy (XPS), showing four peaks at 285.08 eV, 399.08 eV, 531.08 eV and 1134.08 eV, indicating that the synthesized Eu-lu-DPA complex is composed of C, N, O, and Eu elements;

[0045] Attached Figure 3 The excitation wavelength and emission wavelength of the two precursors of the dual-ligand rare earth fluorescent nanoparticles Eu-lu and Eu-DPA obtained in Example 1 are measured. The fluorescence intensity of the complex before and after the complexation is not affected by the ligand complexation;

[0046] Attached Figure 4 The measured spectrum of Eu-lu-DPA synthesized in Example 1 at an excitation wavelength of 265 to 285 nm. Eu-lu-DPA exhibits good red fluorescence and obvious blue luminescence; the fluorescence intensity at 423 nm and 618 nm under different excitation wavelengths and the corresponding ratio I are recorded. 618 / I 423 ;I 616 / I 425 The ratio of is best at an excitation wavelength of 270 nm, so the excitation wavelength of 270 nm is determined to be the optimal excitation wavelength, indicating the successful construction of the dual-emission system.

[0047] Performance Test:

[0048] Attached Figure 5 The stability of the Eu-lu-DPA dual-ligand rare earth fluorescence sensor synthesized in Example 1 was tested. The aqueous solution of Eu-lu-DPA was stored at 4°C for 7, 14, and 21 days, respectively, and the fluorescence spectrum was collected with 270nm excitation. The results showed that the dual-ligand emission probe intensity of Eu-lu-DPA remained unchanged. Due to the high stability and multi-ligand emission of Eu-lu-DPA, it has application prospects in the detection of copper ions.

[0049] Study on the recognition, detection and quantitative analysis of heavy metal copper ions by Eu-lu-DPA:

[0050] Attached Figure 6 Eu-lu-DPA synthesized in Example 1 was exposed to different concentrations of Cu at room temperature. 2+ The fluorescence spectra of Cu ions were further analyzed quantitatively. 2+ Complexation with the coordinated carboxylic acid groups in Eu(DPA)3 results in energy transfer from DPA to Cu via the O-Cu-O bond. 2+ , weakened the transfer to Eu 3+ The red fluorescence weakened with the increase of copper ion concentration, and the red fluorescence significantly weakened, while the blue emission fluorescence remained relatively stable.

[0051] Experimental conditions for quantitative analysis: Anhydrous copper sulfate was dissolved in 5 ml of deionized water to prepare a 0.01 M copper sulfate solution, and the 0.01 M copper sulfate solution was diluted to different concentrations of 0, 5, 10, 15, 20, 25, 30, 35, and 40 μM, respectively, and added to Eu-lu-DPA fluorescent nanoparticles, the mixture was fully shaken and reacted at room temperature for 2 min, and then the fluorescence spectrum was collected with 270 nm excitation;

[0052] Quantitative analysis results of copper ions: The fluorescence intensity at 618nm in the fluorescence spectrum gradually decreases with the increase of copper ion concentration; Figure 7 It can be seen that the F 618 / F 423 The relationship between the fluorescence ratio at and the copper ion concentration, Cu 2+ The ions have a good linear relationship in the concentration range of 0–25 μM, with a correlation coefficient of y=0.1866x-0.03 and R 2 =0.99; therefore, this relationship curve can be used to quantitatively detect the copper ion concentration, (y is I 618 / I 423 The relative decrease of fluorescence ratio, x is the copper ion concentration in water environment);

[0053] Detection limit and sensitivity of Eu-lu-DPA for copper ions: dual-ligand fluorescent nanoparticles I 618 / I 423 The relative decrease in fluorescence ratio showed a good linear relationship with the concentration of copper ions. Therefore, we further calculated the detection limit (LOD) of Eu-lu-DPA for copper ions. The common calculation method for the detection limit is LOD = k × σ, where k represents the confidence factor and σ represents the standard deviation of the blank signal. According to the IUPAC standard, k is 3 here, and σ requires a large number of repeated blank signal fluorescence intensities to be determined. The standard deviation is calculated by the formula. Here we repeatedly measured 9 sets of data. The formula for calculating the standard deviation is as follows:

[0054] Among them, I i is the fluorescence intensity of the blank signal, I a is the average intensity of 9 groups of data, N is the number of repetitions, and the calculated result after 9 repetitions here is σ=0.00209; the final detection limit calculation result LOD=618nM, indicating that this method has high accuracy and low detection limit for detecting copper ions.

[0055] The sensing performance of the dual ligand complex Eu-lu-DPA was tested in the presence of various interfering ions (such as Fe 3+ ) case, the nanoparticles only 2+ It is crucial for the practical application of nanoparticles to respond specifically without reacting to other interfering substances, such as Figure 8 As shown, 300 μM of common interfering ions (Na + , K + 、Ag + , Hg 2+ 、Co 2+ 、Ni 2+ , Ca 2+ Mg 2 + 、Zn 2+ , Fe 3+ 、Al 3+ 、SO4 2- PO4 3- 、Urea、Glu、Cu 2+ ) aqueous solution; the concentration of the interfering substance is Cu 2+ ion concentration is ten times higher than that of the original sample. 100ul of the solution containing the above interfering substances is added to the stock solution containing Eu-lu-DPA. In order to restore the anti-interference ability in the real sample, the solution of the interfering substance uses pure water as the solvent and the pH is not adjusted. When interfering substances exist, most of them have little effect on the fluorescence emission intensity. Among them, Ag, Ni, Zn ions have a slight interference on the fluorescence intensity of Eu-lu-DPA, but due to the high concentration of the interfering substances and the more significant quenching of 30μM copper ions, the content of the interfering substances in the actual sample is far less than that of the copper ions, so it will not have much effect on the detection of copper ions. The fluorescence of Eu-lu-DPA fluorescent nanoparticles is higher than that of F 618 / F 423 The effect is significantly reduced after encountering copper ion mixture, and other species have almost no interference with Cu 2+ These results indicate that the Eu-lu-DPA nanoparticle system has excellent selectivity and anti-interference and can be used as fluorescent nanoparticles to detect Cu in water environment. 2+ .

[0056] In summary, the present invention prepares a ternary dual ligand complex nanoparticle Eu-lu-DPA based on Eu, which is used for high-sensitivity and selective detection of copper ions through photoinduced electrons. The Eu-lu-DPA dual ligand complex not only has high sensitivity and selectivity, but also has a fast fluorescence response speed, and the response can be completed in 50-60 seconds; more importantly, the proposed proportional fluorescence response material can reduce the detection time under complex matrices and environments, and improve the reliability of the detection system; and the nanoparticle is quite simple to manufacture, does not require complex material preparation, all reagents can be purchased from the market, and samples such as tap water and river water only need simple processing, so that the detection can be completed quickly on site; the designed nanoparticles can be accurately analyzed in the range of 0-25μM, and can be detected in real water samples with high detection accuracy; this work will provide a reference for the detection of Cu 2+ It provides fruitful guidance for environmental monitoring and rapid on-site testing of drinking water environments, and provides ideas for the development of hazard detection instruments in real life.

[0057] The above-mentioned embodiments only express the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that all modifications and improvements made to the present invention in accordance with the patent application of the present invention without departing from the concept of the present invention should fall within the scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions, characterized in that: The dual-ligand rare earth fluorescent nanoparticles are used to detect Cu 2+ A lanthanide-based ratiometric fluorescent probe having dual emission sites, wherein the fluorescent probe exhibits strong blue and red fluorescence at 423 nm and 618 nm; The preparation method of the dual-ligand rare earth fluorescent nanoparticles comprises the following steps: (1) dissolving solid europium nitrate in ultrapure water to prepare a europium nitrate solution, adding a DMSO solution containing luminol to the europium nitrate solution, and then adding a PBS buffer solution thereto to obtain a mixture, and stirring the mixture at room temperature for 2 to 3 hours to obtain a clear and transparent solution containing a precursor Eu-Lu complex; (2) Adding a pyridine dicarboxylic acid aqueous solution to the clear transparent solution containing the precursor Eu-lu complex and continuing to stir at room temperature for 2 to 3 hours to obtain a clear solution of the Eu-lu-DPA biligand complex, and storing it at 4° C. before use.

2. The dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions according to claim 1, characterized in that: The molar ratio of europium ions, luminol and dipicolinic acid in the clear solution of the Eu-lu-DPA biligand complex is 1.4:1:1.

2.

3. The dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions according to claim 1, characterized in that: The pH value of the PBS buffer solution needs to be adjusted to 8 using sodium hydroxide.

4. An application of dual-ligand rare earth fluorescent nanoparticles for sensitive detection of copper ions, characterized in that: Use of the dual-ligand rare earth fluorescent nanoparticles for sensitive detection of copper ions as described in any one of claims 1 to 3 in the selective detection of copper ions in an aqueous environment.

5. The use of a dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions as claimed in claim 4, characterized in that: The method for detecting copper ions is as follows: 140 μM / L Eu-lu-DPA is added to solutions with different copper ion concentrations, and after sufficient shaking, a fluorescence spectrum with an excitation wavelength of 270 nm is collected to obtain a fluorescence spectrum change graph of the dual-ligand rare earth fluorescent nanoparticles. The copper ions in the water environment can be quickly and quantitatively detected through the linear relationship of the fluorescence spectrum change graph.

6. The use of a dual-ligand rare earth fluorescent nanoparticle for sensitive detection of copper ions as claimed in claim 5, characterized in that: The fluorescence spectrum change diagram of the dual-ligand rare earth fluorescent nanoparticles takes the copper ion concentration as the abscissa and the fluorescence intensity ratio I as the ordinate. 618 / I 423 A linear relationship diagram is drawn with the relative decrease value of the fluorescence intensity ratio as the ordinate, and each relative decrease value of the fluorescence intensity ratio corresponds to a copper ion concentration. The copper ions in the water environment can be quickly and quantitatively detected through the linear relationship.

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