Preparation method and application of a water-soluble fluorescent probe for detecting mercury ions

Abstract

A method for preparing a water-soluble fluorescent probe for detecting mercury ions and its application relate to the field of analytical detection of mercury ions, and in particular to a method for preparing a water-soluble 1,8-naphthalimide fluorescent probe C and the detection of mercury ions. The invention solves the problem that the test system in the existing mercury ion fluorescent probe detection method needs to be assisted by an organic solvent and cannot achieve green detection in a full water environment. The preparation method of the fluorescent probe C in the present invention is as follows: 4-bromo-N-2-(2-(2-hydroxyethoxy)ethoxy)ethyl-1,8-naphthalimide is refluxed with hydrazine hydrate in ethanol to obtain the result. The fluorescent probe C prepared by the present invention can realize specific fluorescence "off-on" detection of mercury ions in a fully aqueous HEPES buffer solution with a pH of 7.4, and the detection time is short and can resist interference from multiple ions. The fluorescent probe prepared by the present invention can be used for trace detection of mercury ions in water bodies.

Description

Technical Field

[0001] The present invention relates to the field of mercury ion analysis and detection, and in particular to a method for preparing a water-soluble 1,8-naphthalimide fluorescent probe and its application in mercury ion detection. Background Art

[0002] Mercury ions (Hg 2+ ) has important applications in the electronics industry, chemical industry, medical industry, lighting and optical industry. Although mercury ions are widely used, their toxicity cannot be ignored. Excessive exposure to mercury ions can cause serious harm to human health and the environment. Mercury ions released from industrial activities, coal burning, and waste incineration enter the atmosphere and water bodies, and are then accumulated and enriched by organisms. Due to their stability and difficulty in degrading, mercury ions are persistent in ecosystems and pose potential hazards to organisms, including damage to the nervous system, impaired immune system, reproductive system, and damage to the cardiovascular and renal systems. Especially for fetuses and infants, exposure to mercury ions may lead to intellectual retardation and behavioral problems. Therefore, it is particularly important to strengthen the monitoring and management of mercury ion pollution.

[0003] Methods for detecting mercury ions include electrochemical, chromatographic, and fluorescent probe methods. Electrochemical and chromatographic methods require high sample preparation and long detection times, limiting their widespread application. Fluorescent probe methods have attracted considerable attention due to their high sensitivity, rapid response, and good selectivity. However, most reported fluorescent probes for mercury ions typically require the use of organic solvents for detection, which may have adverse environmental impacts, limiting their sustainability and environmental friendliness in practical applications. Therefore, developing fluorescent probes capable of detecting mercury ions in pure water conditions is an important research direction. Pure water fluorescent probes can not only reduce dependence on organic solvents, but also significantly reduce environmental impact, meeting the requirements of sustainable development. However, to achieve this goal, challenges such as fluorescence signal stability, detection sensitivity, and anti-interference ability under pure water conditions need to be overcome, which requires further research.

[0004] 1,8-Naphthalimide is one of the most commonly used fluorophores in the synthesis of fluorescent probes. It not only exhibits excellent chemical and optical stability but also good biocompatibility. Furthermore, the large Stokes shift and ease of modification of 1,8-naphthalimide fluorescent probes are also important advantages. By adjusting the substituents attached to the nitrogen atom of the 1,8-naphthalimide fragment and the 4,5, or 3,4 positions of the naphthalene ring, it can be given good compatibility and specificity, making it widely used in the preparation of fluorescent probes. In this invention, by introducing a long-chain group rich in oxygen atoms into the nitrogen atom of the 4-bromo-1,8-naphthalimide fragment, the hydrophilicity of the probe is increased and a complexing site is created. Furthermore, a hydrazine group is introduced at the 4-position of the naphthalene ring to replace the bromine atom, further improving the water solubility of the probe. Based on this concept, a 1,8-naphthalimide-based fluorescent probe C was designed and prepared. It can realize fluorescent "off-on" detection of mercury ions in pure water. The detection process has the advantages of good specificity, strong interference resistance, rapid response, and low detection limit. It has good application prospects in environmental monitoring. Summary of the Invention

[0005] The present invention aims to solve the problem that the detection system of the existing mercury ion fluorescent probe detection method needs an organic solvent as an auxiliary, and provides a preparation method and application of a fluorescent probe for detecting mercury ions in a pure water system.

[0006] The molecular structure of the water-soluble fluorescent probe C used to detect mercury ions in the present invention is:

[0007]

[0008] The synthetic route of the fluorescent probe C is as follows:

[0009]

[0010] The preparation method of the fluorescent probe C is as follows: 4-bromo-N-2-(2-(2-hydroxyethoxy)ethoxy)ethyl-1,8-naphthalimide and 80w% hydrazine hydrate are refluxed in anhydrous ethanol to obtain the fluorescent probe C.

[0011] Application of the fluorescent probe C of the present invention in the quantitative and qualitative detection of mercury ions.

[0012] Furthermore, fluorescent probe C can realize fluorescence "off-on" detection of mercury ions in pure water.

[0013] Furthermore, when the mercury ion concentration is in the range of 1-11 μM, the fluorescence intensity of the fluorescent probe C is linearly related to the mercury ion concentration, and the linear equation is y=184.04x-63.56, R 2 =0.990, the detection limit of mercury ions is calculated to be 4.53×10 - 8 mol / L.

[0014] Furthermore, the response time of fluorescent probe C to mercury ions is 12 seconds.

[0015] Furthermore, fluorescent probe C can detect mercury ions in tap water, with the recovery rate of mercury ions in actual water samples ranging from 98.10% to 100.39% and the relative standard deviation ranging from 0.17% to 1.16%.

[0016] Principle of the present invention:

[0017] The fluorescent probe C prepared by the present invention does not exhibit fluorescence itself. When the fluorescent probe C interacts with mercury ions, the mercury ions complex with the carbonyl group and ether bond oxygen atoms in the probe molecule, weakening the original photoinduced electron transfer effect. This leads to an enhanced fluorescence effect of the system, ultimately enabling the detection of mercury ions.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) The fluorescent probe C prepared in the present invention can realize the fluorescence detection of mercury ions in pure water. The detection process does not require the assistance of organic solvents, making the fluorescent probe detection method more environmentally friendly.

[0020] 2) The response time of the fluorescent probe C prepared by the present invention to mercury ions is only 12 seconds, the detection speed is fast, and the detection efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention prepares the fluorescent probe C 1 H NMR spectrum;

[0022] Figure 2 The FT-RT spectrum of the fluorescent probe C prepared by the present invention;

[0023] Figure 3 Selective recognition diagram of fluorescent probe C for metal ions;

[0024] Figure 4 The effect of coexisting metal ions on the recognition of mercury ions by fluorescent probe C;

[0025] Figure 5 The effect of coexisting anions on the recognition of mercury ions by fluorescent probe C;

[0026] Figure 6 Linear relationship diagram of fluorescence response of fluorescent probe C to different concentrations of mercury ions;

[0027] Figure 7 Job's plot of fluorescent probe C for mercury ions;

[0028] Figure 8Response time diagram of fluorescent probe C to mercury ions; DETAILED DESCRIPTION

[0029] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0030] Specific embodiment 1: This embodiment is a water-soluble fluorescent probe for detecting mercury ions. The molecular structure of the fluorescent probe C is:

[0031]

[0032] Specific embodiment 2: The preparation method of the fluorescent probe C is as follows: 4-bromo-N-2-(2-(2-hydroxyethoxy)ethoxy)ethyl-1,8-naphthalimide and 80w% hydrazine hydrate are refluxed in anhydrous ethanol.

[0033] Specific embodiment three: Application of the fluorescent probe C in this embodiment in the detection of mercury ions.

[0034] Specific embodiment 4: This embodiment differs from specific embodiment 3 in that the fluorescent probe C can realize fluorescence "off-on" detection of mercury ions. Other aspects are the same as specific embodiment 3.

[0035] Specific embodiment 5: This embodiment differs from specific embodiment 3 or 4 in that: when the mercury ion concentration is in the range of 1-11 μM, the fluorescence intensity of the fluorescent probe C is linearly related to the mercury ion concentration, and the linear equation is y=184.04x-63.56, R 2 =0.990, the detection limit of mercury ions is calculated to be 4.53×10 -8 mol / L. Other aspects are the same as those in the third or fourth embodiment.

[0036] Specific embodiment 6: This embodiment differs from specific embodiments 3 to 5 in that the response time of the fluorescent probe C to mercury ions is 12 seconds. Other aspects are the same as specific embodiments 3 to 5.

[0037] Specific embodiment 7: This embodiment differs from specific embodiments 3 to 6 in that the fluorescent probe C can detect mercury ions in tap water, with a recovery rate of mercury ions in actual water samples of 98.10% to 100.39% and a relative standard deviation of 0.17 to 1.16%. Other aspects are the same as specific embodiments 3 to 6.

[0038] When actually testing samples containing mercury ions, the samples can be pre-treated by centrifugation and filtration to remove solid particle impurities.

[0039] The following embodiments of the present invention are described in detail. The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation plans and specific operating processes, but the protection scope of the present invention is not limited to the following embodiments.

[0040] Example 1: The preparation method of the fluorescent probe C in this example is carried out according to the following steps:

[0041] 4-Bromo-N-2-(2-(2-hydroxyethoxy)ethoxy)ethyl-1,8-naphthalimide (0.3000 g, 0.73 mmol), 80% hydrazine hydrate (0.0736 g, 1.5 mmol) and 10 mL of anhydrous ethanol were added to a 25 mL three-necked flask, and the reaction was stirred at reflux at 80°C until completion. After cooling to room temperature, vacuum filtration and drying were carried out, and washing with ethanol was performed to obtain a red 1,8-naphthalimide fluorescent probe C (0.2129 g) with a yield of 78.3%. 1 H NMR (300MHz, DMSO-d6) δ9.11(s,1H),8.60(d,J=8.4Hz,1H),8.40(d,J=6.4Hz,1H),8.28(d,J=8.6Hz,1H) ,7.62(dd,J=9.0,1.2Hz,1H),7.24(d,J=8.7Hz,1H),4.67(s,2H),4.54(t,J=5.3Hz,1H),4.20(t,J=6.5H z,2H),3.61(t,J=6.6Hz,2H),3.57–3.54(m,2H),3.50–3.46(m,2H),3.41(t,J=3.0Hz,2H),3.38–3.36(m ,2H).IR(KBr)ν:3346,2897,2869,1687,1631,1571,1535,1395,1361,1141,1118,1071,898,773,582cm -1 .

[0042] 1,8-Naphthalimide Fluorescent Probe C 1 H NMR spectrum, FT-RT spectrum such as Figure 1 、 2 shown.

[0043] Example 2: Preparation of fluorescent probe C solution, according to the following steps:

[0044] Accurately weigh 3.6 mg of 1,8-naphthalimide fluorescent probe C and prepare it with methanol to 1.0×10 -2 mol / L mother solution A; take 50 μL of the concentration of 1.0×10 -2 mol / L solution A was diluted to 50 mL with HEPES buffer solution at pH 7.4 to obtain 1.0×10-5 mol / L fluorescent probe C solution.

[0045] Example 3: Selective recognition of metal ions by fluorescent probe C is carried out according to the following steps:

[0046] Take 3mL fluorescent probe C solution, add 3eq. Cu 2+ ,Ba 2+ ,Bi 2+ ,Hg 2+ ,Ca 2+ ,Cd 2+ ,Cr 3+ ,Co 2+ ,K + ,Li 2+ ,Al 3+ ,Mg 2+ ,Na + ,Ni 2+ ,Pb 2+ ,Cs 2+ ,Ce 3+ ,Fe 3+ ,Zn 2+ ,Ag + The fluorescence intensity of the aqueous solution was measured at an excitation wavelength of 351 nm. The results are as follows Figure 3 As shown in the figure, the fluorescence of the system was significantly enhanced after the addition of mercury ions. The addition of copper ions also increased the fluorescence intensity of the system, but the fluorescence enhancement effect was far less than that of mercury ions. However, the fluorescence intensity did not change significantly when other metal ions were added, indicating that the fluorescent probe C solution can achieve specific recognition of mercury ions.

[0047] Example 4: Anti-interference ability of fluorescent probe C for mercury ion recognition was carried out according to the following steps:

[0048] 3eq. of Cu was added to the fluorescent probe C solution. 2+ ,Ba 2+ ,Bi 2+ ,Ca 2+ ,Cd 3+ ,Cr 3+ ,Co 3+ ,K + ,Li 2+ ,Al 3+ ,Mg 2+ ,Na + ,Ni 2+ ,Pb 2+ ,Cs 2+ ,Ce 3+ ,Fe 3+ ,Zn 2+ ,Ag + and anion S2O32- 、SO4 2- 、SO3 2- 、F - PO4 3- 、NO3 - 、I-、CO3 2- 、CN-、CH3COO - 、Cr2O7 2- and P2O7 4- The fluorescence intensity of the aqueous solution was recorded at an excitation wavelength of 351 nm, and then 3 eq. of Hg 2+ aqueous solution, observe and record the changes in fluorescence intensity. The results are as follows Figure 4 、 5 The presence of other metal ions or anions except copper ions will not change the fluorescence of the probe itself. Only copper ions can slightly enhance the fluorescence of the system. However, the presence of EDTA can enhance the fluorescence of the system. 2+ The effect of mercury ions was masked, and the subsequent addition of mercury ions to each system could achieve significant fluorescence enhancement. Therefore, fluorescent probe C has good anti-interference ability for the detection of mercury ions.

[0049] Example 5: Detection limit of mercury ions by fluorescent probe C, performed according to the following steps:

[0050] Take 3mL of the solution with a concentration of 1.0×10 -5 mol / L fluorescent probe C solution, and 3 μL of 1×10 -3 mol / L mercury ion aqueous solution, measure the fluorescence intensity, the result is as follows Figure 6 As shown. When the mercury ion concentration is within the range of 0μM-15μM, the fluorescence intensity increases with the increase of mercury ion concentration. In addition, within the range of 1μM-11μM, the fluorescence intensity of probe C shows a good linear relationship with the mercury ion concentration, and the fitting equation is y=184.04x-63.56, R 2 =0.990. According to the calculation formula of detection limit 3σ / k, the detection limit of fluorescent probe C for mercury ions is calculated to be 4.53×10 -8 mol / L, indicating that fluorescent probe C can realize trace detection of mercury ions and has good detection sensitivity.

[0051] Example 6: The interaction between fluorescent probe C and mercury ions was carried out according to the following steps:

[0052] The total concentration of fluorescent probe C and mercury ions in the detection system was maintained at 1×10 -5 mol / L remains unchanged. By changing the equivalent ratio of fluorescent probe C and mercury ions, the fluorescence intensity is measured and the Job's Plot curve is drawn. The results are shown in the figure. Figure 7When the molar fraction of mercury ions is 0.48, the fluorescence intensity shows an inflection point, indicating that the interaction ratio between fluorescent probe C and mercury ions is 1:1.

[0053] Example 7: The response time of fluorescent probe C to mercury ions was determined by the following steps:

[0054] Take 3mL of the solution with a concentration of 1.0×10 -5 mol / L fluorescent probe C solution, add 1 equivalent concentration of 1×10 -2 mol / L mercury ion aqueous solution, measure the fluorescence intensity every three seconds, and record the results as follows Figure 8 As shown in Figure 2, after the addition of mercury ions, the fluorescence intensity of the system increased rapidly within the first 6 seconds and stabilized at approximately 12 seconds. This indicates that probe C can quickly recognize mercury ions.

[0055] Example 8: Application of fluorescent probe C in detecting mercury ions in actual water samples

[0056] To investigate the potential application of fluorescent probe C in real-world applications, laboratory tap water samples were pretreated: the water samples were centrifuged at 12,000 rpm for 10 minutes and filtered through a 0.45 μm filter. Mercury ion solutions with concentrations of 4 μmol / L, 6 μmol / L, 8 μmol / L, and 10 μmol / L were prepared. These mercury ion solutions were added to the fluorescent probe C solutions. Under an excitation wavelength of 351 nm, the peak fluorescence emission intensity of the fluorescent probe at 400 nm was measured and substituted into the following equation to calculate the concentration of the mercury ion solution. The test results are shown in Table 1.

[0057] y=184.04x-63.56

[0058] Wherein, X is the mercury ion concentration and Y is the fluorescence emission peak intensity value.

[0059] Table 1 Detection of mercury ions by fluorescent probe C in actual water samples

[0060] Actual water sample Addition amount (μmol / L) Detection amount (μmol / L) Recovery rate (%) RSD (%) blank / / / 1.60 1 (tap water) 4 3.92 98.10 0.27 2 (tap water) 6 6.02 100.39 1.16 3 (tap water) 8 7.97 99.61 0.38 4 (tap water) 10 9.96 99.57 0.17

[0061] As shown in Table 1, the recovery rate of mercury ions in actual water samples ranged from 98.10% to 100.39%, with a relative standard deviation of 0.17% to 1.16%. The measured mercury ion concentrations had a very small error compared to the corresponding spiked concentrations. These results demonstrate that the fluorescent probe C prepared in the present invention has good accuracy in detecting mercury ions in actual water samples and can quantitatively detect mercury ions in the range of 1 to 11 μmol / L, demonstrating excellent practical performance.

Claims

1. A water-soluble fluorescent probe for detecting mercury ions, characterized in that The molecular structure of fluorescent probe C is:

2. The method for preparing a water-soluble fluorescent probe for detecting mercury ions according to claim 1, wherein 4-Bromo-N-2-(2-(2-hydroxyethoxy)ethoxy)ethyl-1,8-naphthalimide was reacted with 80w% hydrazine hydrate in ethanol under reflux.

3. Use of the fluorescent probe C as claimed in claim 1 in the quantitative and qualitative detection of mercury ions for purposes other than diagnosis and treatment of diseases.

4. The use according to claim 3, characterized in that Fluorescent probe C can realize fluorescent "off-on" detection of mercury ions in a pure water environment.

5. The use according to claim 3, characterized in that When the mercury ion concentration is in the range of 1-11 μM, the fluorescence intensity of fluorescent probe C is linearly related to the mercury ion concentration, and the linear equation is y=184.04x-63.56, R 2 =0.990, the detection limit of mercury ions is calculated to be 4.53×10 -8 mol / L.

6. The use according to claim 3, characterized in that The response time of fluorescent probe C to mercury ions is 12 seconds.

7. The use according to claim 3, characterized in that Fluorescent probe C can detect mercury ions in tap water. The recovery rate of mercury ions in actual water samples is 98.10% to 100.39%, and the relative standard deviation is 0.17 to 1.16%.

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