Fluorescent probe for detecting lead ions as well as preparation method and application of fluorescent probe
By designing a fluorescent probe of pyridinamide bis Schiff alkali secondary amine, the problem of poor selectivity and sensitivity of Pb2+ in the prior art is solved, and the detection of lead ion with high selectivity and high sensitivity in water environment is achieved, which has wide application value.
Patent Information
- Application Number
- CN202510190184.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-06-06
AI Technical Summary
The existing fluorescent probes that recognize Pb2+ have poor selectivity and sensitivity, making it difficult to efficiently identify lead ions in water environments.
A fluorescent probe of pyridinamide bis Schiff alkali secondary amine was designed, which was prepared by one-pot condensation reaction and reduction reaction, with high selectivity and sensitivity.
In the water environment, Pb2+ can be identified with high selectivity and is not disturbed by other metal ions. The detection limit is 1.054683×10-8mol/L, which is suitable for the preliminary detection of Pb2+ pollution in the water system.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of heavy metal detection, and in particular to a fluorescent probe for detecting lead ions, and a preparation method and application thereof. Background Art
[0002] Lead is a toxic heavy metal that is extremely harmful to the human body. Therefore, when lead and its compounds enter the body, they will cause damage to multiple systems such as the nervous system, hematopoietic system, digestive system, kidney system, cardiovascular system and endocrine system. If the content is too high, it will cause lead poisoning. Children with lead poisoning will experience developmental delay, loss of appetite, difficulty walking, constipation, and insomnia; others will be accompanied by hyperactivity, hearing impairment, inattention and mental retardation. With the rapid development of the industrial market, lead has been widely used in all walks of life. At present, lead mainly affects human health through food, drinking water, air and other means. Therefore, studying the method of determining trace lead content has positive scientific significance.
[0003] The researchers designed a Pb 2+ Most fluorescent probe molecules are of the fluorescence quenching type. Fluorescence quenching probe detection has the disadvantages of large background signal, low sensitivity, poor selectivity, and is not suitable for biological sample detection. Summary of the invention
[0004] In view of the technical problems existing in the background technology, the present application provides a fluorescent probe for detecting lead ions and a preparation method and application thereof, aiming to solve the existing problems of identifying Pb 2+ Technical problems of poor selectivity and sensitivity of fluorescent probes.
[0005] In a first aspect, the embodiments of the present application provide a fluorescent probe for detecting lead ions, wherein the fluorescent probe is a pyridineamide bis-Schiff base secondary amine, and its structural formula is: .
[0006] In a second aspect, an embodiment of the present application provides a method for preparing a fluorescent probe for detecting lead ions. The fluorescent probe is o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide, which are prepared by a one-pot condensation reaction and a reduction reaction.
[0007] In some embodiments, the steps include: S1, adding o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide to an alcohol solution, heating under reflux to react, and obtaining a pyridineamide bis-Schiff base alcohol solution; S2, after cooling the pyridine amide bis-Schiff base alcohol solution, adding a reducing agent solution and stirring the reaction, evaporating the solvent, adding water and stirring the reaction, extracting, washing, drying, and removing the solvent to obtain a crude product of pyridine amide bis-Schiff base secondary amine; S3. The crude product of pyridineamide bis-Schiff base secondary amine is recrystallized with ethanol, and the filter cake is collected after cooling and filtering to obtain a fluorescent probe for detecting lead ions.
[0008] In some embodiments, the alcohol solution in step S1 is one or more of methanol, ethanol or isopropanol.
[0009] In some embodiments, the heating reflux reaction conditions in step S1 are: the heating reflux temperature is 65-80° C., and the reaction time is 5-7 hours.
[0010] In some embodiments, in step S2, the pyridinamide bis-Schiff base alcohol solution is cooled to below 20° C. using an ice-water bath or an ice-salt bath, and the reducing agent solution is added to the cooled pyridinamide bis-Schiff base alcohol solution, and the reaction is stirred for more than 12 hours.
[0011] In some embodiments, a reducing agent is dispersed in methanol or ethanol to obtain a reducing agent solution; the reducing agent includes NaBH 4 , NaBH 3 CN, Na(OAc) 3 One or more of BH; the molar ratio of the reducing agent to the pyridineamide bis Schiff base alcohol is (3~5):1.
[0012] In a third aspect, the present application provides an application of a fluorescent probe for detecting lead ions, using a fluorescent probe for detecting lead ions to detect Pb 2+ Conduct qualitative or quantitative analysis.
[0013] In some embodiments, the fluorescent probe for detecting lead ions is Pb 2+ The qualitative analysis includes the following steps: Dispersing the fluorescent probe in deionized water, and adjusting the volume to obtain a fluorescent probe solution, wherein the concentration of the fluorescent probe is 7.5-10 μmol / L; The fluorescent probe and the sample to be tested are mixed evenly, the molar concentration of metal ions in the sample to be tested is more than twice that of the fluorescent probe, the reaction is carried out for more than 5 minutes, and the volume is fixed to obtain a sample solution; The fluorescence intensity A1 of the fluorescent probe solution is tested by a fluorescence spectrometer at an emission wavelength of 330 nm, and then the fluorescence intensity A2 of the sample solution is tested. If A2 is greater than or equal to 5A1, it can be determined that the sample contains Pb. 2+ Otherwise, it is determined that the sample does not contain Pb 2+ .
[0014] In some embodiments, the fluorescent probe for detecting lead ions is 2+ The quantitative analysis includes the following steps: Prepare gradient concentrations of Pb2+ Solution, to Pb 2+ Fluorescent probes were added to the solution to detect the Pb 2+ The fluorescence intensity of the solution at an emission wavelength of 330 nm was used to construct a relationship between the fluorescence intensity and Pb 2+ The fluorescence probe was mixed with the sample to be tested for more than 5 minutes to obtain a sample solution, and the fluorescence intensity of the sample solution at an emission wavelength of 330nm was detected. The Pb content in the sample solution was calculated according to the standard curve. 2+ content; Fluorescent probe for Pb 2+ The detection limit is 1.054683×10 -8 mol / L.
[0015] Different from the existing technical solutions, the beneficial effects of this application include: 1. The present application provides a pyridineamide bis-Schiff base secondary amine fluorescent probe for lead ion detection, which is a Pb 2+ Fluorescent probe, which can detect Pb in water environment system 2+ It has high selective recognition, is not interfered by other metal ions in aqueous solution, and has strong interference ability.
[0016] 2. This application can be applied to Pb in water system 2+ In the early detection of pollution, it can sensitively detect trace amounts of Pb in the water phase 2+ ions, the detection limit was 1.054683×10 -8 mol / L, the complex constant is 7.2727×10 7 (mol / L) -1 , and has low toxicity, so it has great application value in the fields of chemical industry, environment, biomedicine, etc.
[0017] 3. This fluorescent probe can identify Pb 2+ ions, the fluorescence enhancement effect can be shown in the pH range of 5 to 9. The fluorescent probe has a rapid recognition response and can complete the detection of Pb in a water system environment within 5 minutes. 2+ The synthetic raw materials of the fluorescent probe are simple and easy to obtain, the cost is low, the conditions are mild, the steps are simple, the product separation and purification are simple, and the yield is as high as 72~81%.
[0018] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0020] Figure 1 This is the fluorescence emission spectrum of the fluorescent probe L in aqueous solution in Example 1 of the present application; Figure 2 As the fluorescent probe L with Pb 2+ Fluorescence emission spectra with increasing concentrations; Figure 3 As a fluorescent probe L for detecting Pb 2+ The standard curve of Figure 4 As the fluorescent probe L 2+ Benesi-Hildebrand linear analysis curve of fluorescence emission with increasing concentration; Figure 5 L and Pb 2+ The total concentration is 10 μmol / L, job diagrams of different complexation ratios; Figure 6 L and Pb 2+ Fluorescence emission graphs in solutions with different pH values; Figure 7 L and Pb 2+ Fluorescence emission graphs with different time responses; Figure 8 The fluorescence emission spectrum changes after adding 20 μmol / L of each metal ion to the fluorescent probe L (10 μmol / L); Fig. 9 Add 20 μmol / L Pb to the fluorescent probe L (10 μmol / L) 2+ Changes in fluorescence emission spectra after coexistence of different metal ions with 20 μmol / L. DETAILED DESCRIPTION
[0021] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.
[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.
[0023] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.
[0024] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.
[0025] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.
[0026] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).
[0027] The researchers designed a Pb 2+ Most fluorescent probe molecules are of the fluorescence quenching type. Fluorescence quenching probe detection has the disadvantages of large background signal, low sensitivity, poor selectivity, and is not suitable for biological sample detection.
[0028] In order to solve the technical problems of large background signal, low sensitivity, poor selectivity and unsuitability for biological sample detection in fluorescence quenching probe detection, the present application provides a fluorescent probe for detecting lead ions and its preparation method and application. The fluorescent probe of the present application is a Pb containing pyridine fluorescent group. 2+ Fluorescent probe, which can detect Pb in water environment system 2+ It has high selective recognition, is not interfered by other metal ions in aqueous solution, and has strong interference ability.
[0029] In a first aspect, the embodiments of the present application provide a fluorescent probe for detecting lead ions, wherein the fluorescent probe is a pyridineamide bis-Schiff base secondary amine, and its structural formula is: .
[0030] In a second aspect, an embodiment of the present application provides a method for preparing a fluorescent probe for detecting lead ions. The fluorescent probe is o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide, which are prepared by a one-pot condensation reaction and a reduction reaction.
[0031] In some embodiments, the steps include: S1, adding o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide to an alcohol solution, heating under reflux to react, and obtaining a pyridineamide bis-Schiff base alcohol solution; S2, after cooling the pyridine amide bis-Schiff base alcohol solution, adding a reducing agent solution and stirring the reaction, evaporating the solvent, adding water and stirring the reaction, extracting, washing, drying, and removing the solvent to obtain a crude product of pyridine amide bis-Schiff base secondary amine; S3. The crude product of pyridineamide bis-Schiff base secondary amine is recrystallized with ethanol, and the filter cake is collected after cooling and filtering to obtain a fluorescent probe for detecting lead ions.
[0032] In some embodiments, the alcohol solution in step S1 is one or more of methanol, ethanol or isopropanol.
[0033] In some embodiments, the heating reflux reaction conditions in step S1 are: the heating reflux temperature is 65-80° C., and the reaction time is 5-7 hours.
[0034] In some embodiments, in step S2, the pyridinamide bis-Schiff base alcohol solution is cooled to below 20° C. using an ice-water bath or an ice-salt bath, and the reducing agent solution is added to the cooled pyridinamide bis-Schiff base alcohol solution, and the reaction is stirred for more than 12 hours.
[0035] In some embodiments, a reducing agent is dispersed in methanol or ethanol to obtain a reducing agent solution; the reducing agent includes NaBH 4 , NaBH 3 CN, Na(OAc) 3 One or more of BH; the molar ratio of the reducing agent to the pyridineamide bis Schiff base alcohol is (3~5):1.
[0036] In a third aspect, the present application provides an application of a fluorescent probe for detecting lead ions, using a fluorescent probe for detecting lead ions to detect Pb 2+Conduct qualitative or quantitative analysis.
[0037] In some embodiments, the fluorescent probe for detecting lead ions is Pb 2+ The qualitative analysis includes the following steps: Dispersing the fluorescent probe in deionized water, and adjusting the volume to obtain a fluorescent probe solution, wherein the concentration of the fluorescent probe is 7.5-10 μmol / L; The fluorescent probe and the sample to be tested are mixed evenly, the molar concentration of metal ions in the sample to be tested is more than twice that of the fluorescent probe, the reaction is carried out for more than 5 minutes, and the volume is fixed to obtain a sample solution; The fluorescence intensity A1 of the fluorescent probe solution is tested by a fluorescence spectrometer at an emission wavelength of 330 nm, and then the fluorescence intensity A2 of the sample solution is tested. If A2 is greater than or equal to 5A1, it can be determined that the sample contains Pb. 2+ Otherwise, it is determined that the sample does not contain Pb 2+ .
[0038] In some embodiments, the fluorescent probe for detecting lead ions is 2+ The quantitative analysis includes the following steps: Prepare gradient concentrations of Pb 2+ Solution, to Pb 2+ Fluorescent probes were added to the solution to detect the Pb 2+ The fluorescence intensity of the solution at an emission wavelength of 330 nm was used to construct a relationship between the fluorescence intensity and Pb 2+ The fluorescence probe was mixed with the sample to be tested for more than 5 minutes to obtain a sample solution, and the fluorescence intensity of the sample solution at an emission wavelength of 330nm was detected. The Pb content in the sample solution was calculated according to the standard curve. 2+ content; Fluorescent probe for Pb 2+ The detection limit is 1.054683×10 -8 mol / L.
[0039] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.
[0040] 1. Preparation method Example 1 A method for synthesizing a pyridineamide bis-Schiff base secondary amine fluorescent probe (L) for heavy metal lead ion detection. The fluorescent probe is o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide, which are obtained by a one-pot condensation reaction and a reduction reaction. The reaction equation is as follows: .
[0041] The synthesis method specifically comprises the following steps: 1) Dissolve 4 mmol of the intermediate N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide Ia in 40 mL of ethanol and add it dropwise to 8.8 mmol of o-anisaldehyde in 40 mL of ethanol at a rate of 5-6 s / d under magnetic stirring. After heating under reflux for about 5 h, stop heating and cool to room temperature.
[0042] 2) Use an ice water bath to control the temperature at 20°C and dissolve 3 times the molar number of NaBH 4 Place 20 mL of ethanol solution in a constant pressure funnel and slowly add it to the cooled reaction solution. After the addition is complete, continue to stir and react for 12 hours; evaporate most of the solvent at normal pressure and reduce the pressure to dryness, then add 60 mL of distilled water and stir to react for 10 minutes, then extract the reaction solution three times with 30 mL of ethyl acetate, and combine the extracts; after washing three times with 30 mL of water, combine the organic layers and dry over anhydrous sodium sulfate.
[0043] 3) The solvent was evaporated to obtain a crude product, which was recrystallized from 20 mL of anhydrous ethanol to obtain a pure product, i.e., the target product, amide-based bis-Schiff base secondary amine fluorescent probe, with a yield of 75%.
[0044] Example 2 Fluorescence emission spectrum test of fluorescent probe: According to the concentration of the fluorescent probe L in Example 1 of 10 μmol / L, the fluorescent probe was added into deionized water and its fluorescence emission spectrum was detected.
[0045] Embodiments 3 to 10 The fluorescent probe prepared in Example 1 is effective for Pb 2+ The sensitivity test of ion selectivity is as follows: According to the concentration of fluorescent probe L of 10μmol / L, the fluorescent probe was added to deionized water, and then 2μmol / L, 4μmol / L, 8μmol / L, 10μmol / L, 20μmol / L, 30μmol / L, 40μmol / L, and 50μmol / L of Pb were added respectively. 2+ , mix well, respond for 5 minutes, and test its fluorescence emission spectrum at 330nm.
[0046] Embodiments 11 to 19 The fluorescent probe prepared in Example 1 is effective for Pb 2+ The complexation ratio test of ions is as follows: The Job's Plot method was used, that is, the probe molecules L and Pb were fixed. 2+ The total concentration of Pb is 10 μmol / L. 2+ The mole fraction in the system increases continuously from 0.1 to 0.9, that is, the fluorescence probe L and Pb 2+ The molar concentration ratios were 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1, respectively, and the fluorescence intensity of the nine samples was measured at 330 nm.
[0047] Embodiments 20 to 29 The fluorescent probe prepared in Example 1 is effective for Pb 2+ Fluorescence emission test in solutions with different pH values, the specific method is as follows: According to the concentration of the fluorescent probe L in Example 1 being 10 μmol / L, the fluorescent probe was added to deionized water to obtain several sample solutions, and the pH of the sample solutions was adjusted to 2, 3, 4, 5, 6, 6.5, 7, 7.5, 8, and 9 using acid or alkali, respectively, to detect the fluorescence emission intensity at 330 nm with a response time of 5 min.
[0048] Embodiment 30 The fluorescent probe prepared in Example 1 is effective for Pb 2+ The fluorescence emission test of the response at different times is as follows: According to the concentration of the fluorescent probe L in Example 1 being 10 μmol / L, the fluorescent probe was added to deionized water to obtain several sample solutions, and the fluorescence emission intensity thereof at 330 nm was detected every 1 min. The fluorescence emission intensity thereof at 330 nm with a response time of 0 to 10 min was detected.
[0049] Embodiment 31 Pb in tap water 2+ Concentration detection, the specific method is as follows: Take the tap water sample and directly mix it with the probe's anhydrous ethanol stock solution (1.00×10 -4 mol·L -1 ) were mixed and the fluorescence emission intensity at 330 nm was detected after 5 min of response.
[0050] Embodiment 32 Pb in tap water 2+ The specific method of the recovery test is as follows: Take the tap water sample and directly mix it with the probe's anhydrous ethanol stock solution (1.00×10 -4 mol·L -1 ) and then add 5 μmol of Pb 2+ After 5 minutes of response, the fluorescence emission intensity at 330 nm was detected.
[0051] Embodiment 33 Pb in the water of Huangjia Lake in Wuhan 2+ Concentration detection: the detection method is the same as in Example 9.
[0052] Embodiment 34 Pb in the water of Huangjia Lake in Wuhan 2+ The recovery test was carried out using the same test method as in Example 10.
[0053] Comparative Examples 1 to 11 The fluorescence emission spectra of the fluorescent probe L prepared in Example 1 after reacting with different metal ions were tested. The specific method is as follows: The test temperature of the fluorescence spectrum was 25°C and the test conditions were deionized water buffer system. Before the test, the metal ions (nitrate or hydrochloride) were prepared into 1×10 -3 mol / L stock solution. During the test, 100uL of a 1×10 -3 mol / L probe molecule L solution into a series of 10mL volumetric flasks, and then transfer 2 times the moles of the corresponding metal ion (K + Mg 2+ , Ca 2+ , Mn 2+ , Cu 2+ 、Zn 2+ , Pb 2+ , Hg 2+ 、Cd 2+ 、Co 2+ Cr 3+ ) solution, add 1 mL of deionized water, react for 5 minutes, and dilute to 1 × 10 -5 mol / L, and test after thorough mixing.
[0054] Comparative Examples 12~22 The fluorescent probe L prepared in Example 1 was tested for resistance to metal ion interference as follows: First add 20 μmol / L Pb into deionized water. 2+ Then, add Pb 2+ The concentration of K + Mg 2+ , Ca 2 + 、Zn2+ , Cu 2+ 、Zn 2+ , Hg 2+ , Mn 2+ 、Cd 2+ Cr 3+ 、Co 2+ The coexisting metal ions were mixed evenly and then the probe molecule L with a concentration of 10 μmol / L was added. The reaction was continued for 5 minutes and the volume was fixed. Then the fluorescence intensity at 330 nm was measured.
[0055] II. Analysis of test results of various embodiments and comparative examples (1) Infrared spectroscopy, mass spectrometry, elemental analysis and fluorescence in deuterated dimethyl sulfoxide (DMSO) solvent of the pyridinamide bis-Schiff base secondary amine fluorescence enhanced molecular probe for lead ion detection prepared in Example 1 1 The H NMR spectrum data are as follows: IR(KBr / cm -1 ): 3309(υN-H), 1666(amideI), 1601(NH), 1362(CN), 1538(amideII), 1463, 1242(pyridyl), 1048, 1028(OCH 3 ), 754, 683 (phenyl), UV-vis (λmax / nm) (ε), 288 (14382); Fluorescence: Em ( 330), Ex ( 325), I (24.66%); 1H NMR (300 MHz, DMSO-d6) δ: 9.25 (H, amide), 4.67 (s, H, amide), 3.54 (s, 2H, -CNH), 8.25 (s, H, pyridylH); 7.25 (m, J = 6.8 Hz, 2H, pyridyl H; 4H, phenyl H), 6.85 (m, J = 7.2 Hz, 4H, phenyl H), 2.35 (s, 6H, OCH3), 3.75(q, J = 6.8 Hz, 8H,-NH-CH 2 -CH 2 -NH), 2.75 (s, 4H, NCH 2 Ph); EI-MS m / Z (%): 492.2(M+H) + . Anal. Calcd for C 27 H 33 N 5 O 4:C 65.99, H 6.72, N14.26; Found: C 66.54, H 6.48, N 14.08%.
[0056] From the above data, it can be seen that the structure of the pyridinamide bis-Schiff base secondary amine fluorescence-enhanced molecular probe for lead ion detection prepared in this example is as follows: .
[0057] (2) The fluorescence emission spectrum obtained in Example 2 is as follows Figure 1 As shown by Figure 1 It can be seen that the fluorescent probe prepared in this example has an emission peak at 330 nm and a strong fluorescence intensity.
[0058] (3) Different Pb 2+ The fluorescence emission spectra at the concentration Figure 2 As shown, from Figure 2 It can be seen that the fluorescence intensity of the fluorescent probe L increases with the Pb 2+ As the concentration of Pb increases, the fluorescence intensity increases continuously, and the fluorescence intensity is similar to that of Pb 2+ The concentration change of Pb 2+ When the concentration increased to 2 equivalents, the fluorescence intensity hardly changed and reached the highest level.
[0059] With different Pb in Examples 3 to 10 2+ Fluorescence emission intensity data at 330nm under different concentrations, with the horizontal axis being Pb 2+ The concentration C is in μmol / L, and the ordinate is the fluorescence intensity F. The fluorescent probe L is used to detect Pb 2+ The standard curve is shown in Figure 3 , Figure 3 The linear equation of the fitting is: F=236.53074+96.06295C; the correlation coefficient is R 2 =0.99939, SD=1.01316. The formula for calculating the limit of detection is LOD=3σ / K, where σ is the standard deviation SD and K is the slope of the fitting line. By calculation, it can be concluded that the fluorescence probe L is effective for Pb 2+ The detection limit is 1.054683×10 -8 mol / L.
[0060] Figure 4 In Examples 3 to 10, the fluorescent probe L follows Pb 2+ Benesi-Hildebrand linear analysis of fluorescence emission with increasing concentration, expressed as 1 / C(Pb 2+ ) is the horizontal axis, 1 / (F-F 0) as the ordinate, the fitted linear equation is: F = 236.53074 + 96.06295C; According to the fluorescence titration data, the BenesiHildebrand equation based on 1:1 was used, and the fitting showed a straight line, indicating that the probe L and Pb 2+ The complexation ratio is 1:1, and the R 2 is 0.99875, and the complex constant is the inverse of the slope of the fitting line. The complex constant K is calculated to be 7.2727×10 7 (mol / L) -1 .
[0061] The carbon dots designed by Yi Minna's research group in the paper "A new dual-emission carbon dot ratiometric fluorescent probe for rapid detection of lead ions" are effective for Pb 2+ The detection limit is 0.0136 mg / L, and the detection range is 0~0.5 mg / L. The probe designed and synthesized by Ren Zehua's research group in "Synthesis of rare earth ion fluorescent probes and their application in lead ion recognition" is effective for Pb 2+ The detection range is between 0 and 24 μmol / L, and the detection limit is 0.13 μmol / L. Compared with the above lead ion probes, the probe in this application has a wide detection range and a low detection limit.
[0062] (4) According to the method of Examples 11 to 19, obtain Figure 5 The fluorescent probe of Example 1 detects Pb 2+ The Job's curve is drawn with the complexation ratio of x(Pb 2+ ), indicating the molar fraction; the ordinate is the fluorescence intensity. 2+ When the molar fraction of Pb is 0.5, the complex has the maximum fluorescence intensity at 330nm. 2+ The complexation ratio is 1:1.
[0063] (6) According to the method of Examples 20 to 29, obtain Figure 6 The fluorescent probe L of Example 1 and Pb 2+ Fluorescence emission diagrams in solutions with different pH values show that the probe molecule L and Pb 2+ The optimal detection pH range is 6.5~7.5.
[0064] (7) According to the method of Example 30, obtain Figure 7 The fluorescent probe L of Example 1 and Pb 2+ The fluorescence emission diagrams of different time responses show that the probe molecule L and Pb 2+ The response time is 5 minutes.
[0065] (8) The test data of Examples 31 to 34 are shown in Table 1 below. The Pb of Examples 31 to 34 was calculated according to the linear equation obtained in Examples 3 to 10. 2+ Detection value, and calculate the recovery rate = (Pb 2+ Detection value / Pb 2+ Addition amount) × 100%, the calculation data is shown in Table 1 below.
[0066] Table 1 Pb in tap water and Huangjiahu River water in Wuhan 2+ Recovery test data
[0067] As can be seen from Table 1, probe L cannot detect Pb in these two actual water samples. 2+ This is because the Pb in the actual water sample 2+ The content is lower than the detection limit of this method; the test results of Examples 31 to 34 are in good agreement with the theoretical addition amount, and the recovery rate is high. Therefore, the fluorescent probe L can be applied to the detection of Pb in actual water samples. 2+ Detection.
[0068] (9) In Comparative Examples 1 to 11, the fluorescence emission spectra of the fluorescent probe L prepared in Example 1 after reacting with different metal ions were obtained. Figure 8 .from Figure 8 It can be seen that after adding different metal ions, the characteristic emission peaks have no obvious changes. 2+ When the fluorescence intensity is increased by 6 times, 2+ Ions have good selectivity and recognition ability.
[0069] (10) The fluorescence intensity of the fluorescent probe L in Examples 12 to 22 at 330 nm under the interference of different coexisting metal ions is shown in Table 1. Fig. 9 .from Fig. 9 It can be seen that other common metal ions (Ca 2+ ,Co 2+ , K + ,Mg 2+ , Hg 2+ ) and Pb 2+ At the same time, Pb 2+ It can still enhance the fluorescence intensity of the fluorescent probe, but Cd 2+ , Zn 2+ , Cu 2+ ,Cr 3+ The presence of ions significantly reduces the fluorescence intensity of the system, which has a certain impact on the accuracy of the detection results.
[0070] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.
Claims
1. A fluorescent probe for detecting lead ions, characterized in that: The fluorescent probe for detecting lead ions is pyridineamide bis-Schiff base secondary amine, and its structural formula is: 。 2. The method for preparing a fluorescent probe for detecting lead ions according to claim 1, characterized in that: The fluorescent probe is prepared from o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide by a one-pot method through condensation reaction and reduction reaction.
3. The method for preparing a fluorescent probe for detecting lead ions according to claim 2, characterized in that: The steps include: S1, adding o-anisaldehyde and N,N'-bis(2-aminoethyl)-2,6-pyridinedicarboxamide to an alcohol solution, heating under reflux to react, and obtaining a pyridineamide bis-Schiff base alcohol solution; S2, after cooling the pyridine amide bis-Schiff base alcohol solution, adding a reducing agent solution and stirring the reaction, evaporating the solvent, adding water and stirring the reaction, extracting, washing, drying, and removing the solvent to obtain a crude product of pyridine amide bis-Schiff base secondary amine; S3, the crude product of the pyridineamide bis-Schiff base secondary amine is recrystallized with ethanol, and the filter cake is collected after cooling and filtering to obtain a fluorescent probe for detecting lead ions.
4. The method for preparing a fluorescent probe for detecting lead ions according to claim 3, characterized in that: The alcohol solution in step S1 is one or more of methanol, ethanol or isopropanol.
5. The method for preparing a fluorescent probe for detecting lead ions according to claim 3, characterized in that: The heating reflux reaction conditions in step S1 are: heating reflux temperature is 65-80° C., and reaction time is 5-7 h.
6. The method for preparing a fluorescent probe for detecting lead ions according to claim 3, characterized in that: In step S2, the pyridinamide bis-Schiff base alcohol solution is cooled to below 20° C. using an ice-water bath or an ice-salt bath, and the reducing agent solution is added to the cooled pyridinamide bis-Schiff base alcohol solution, and the reaction is stirred for more than 12 hours.
7. The method for preparing a fluorescent probe for detecting lead ions according to claim 3, characterized in that: The reducing agent is dispersed in methanol or ethanol to obtain the reducing agent solution; the reducing agent includes one or more of NaBH4, NaBH3CN, and Na(OAc)3BH; the molar ratio of the reducing agent to pyridineamide bis-Schiff base alcohol is (3-5):
1.
8. An application of a fluorescent probe for detecting lead ions, characterized in that: The fluorescent probe for detecting lead ions described in claim 1 is used to detect Pb 2+ Conduct qualitative or quantitative analysis.
9. The use of the fluorescent probe for detecting lead ions according to claim 8, characterized in that: The fluorescent probe for detecting lead ions is 2+ The qualitative analysis includes the following steps: Dispersing the fluorescent probe in deionized water, and adjusting the volume to obtain a fluorescent probe solution, wherein the concentration of the fluorescent probe is 7.5-10 μmol / L; The fluorescent probe and the sample to be tested are mixed evenly, the molar concentration of metal ions in the sample to be tested is more than twice that of the fluorescent probe, the mixture is reacted for more than 5 minutes, and the volume is fixed to obtain a sample solution; The fluorescence intensity A1 of the fluorescent probe solution is tested by a fluorescence spectrometer at an emission wavelength of 330 nm, and then the fluorescence intensity A2 of the sample solution is tested. If A2 is greater than or equal to 5A1, it can be determined that the sample contains Pb. 2+ Otherwise, it is determined that the sample does not contain Pb 2+ .
10. The use of the fluorescent probe for detecting lead ions according to claim 8, characterized in that: The fluorescent probe for detecting lead ions is 2+ The quantitative analysis includes the following steps: Prepare gradient concentrations of Pb 2+ Solution, to Pb 2+ Fluorescent probes were added to the solution to detect the Pb 2+ The fluorescence intensity of the solution at an emission wavelength of 330 nm was used to construct a relationship between the fluorescence intensity and Pb 2+ The fluorescent probe was mixed with the sample to be tested for more than 5 minutes to obtain a sample solution, and the fluorescence intensity of the sample solution at an emission wavelength of 330nm was detected. The Pb content in the sample solution was calculated according to the standard curve. 2+ content; The fluorescent probe is for Pb 2+ The detection limit is 1.054683×10 -8 mol / L.