A fluorescent probe for detecting electrolyte viscosity, its preparation method and application

Abstract

This invention relates to a fluorescent probe for detecting electrolyte viscosity, its preparation method, and its application, belonging to the field of trace element analysis technology in electrolytes. The fluorescent probe TV has the chemical structure shown in formula (I). 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde and a benzoindole derivative are dissolved in anhydrous ethanol. After adding an organic base catalyst, the system is refluxed and stirred under a nitrogen atmosphere, precipitating a solid. The solid is then filtered and dried to obtain the target product, the fluorescent probe. This fluorescent probe exhibits a sensitive fluorescence response to electrolyte viscosity, enabling efficient rapid detection of electrolyte viscosity. Furthermore, the synthesis method is simple and rapid, suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of trace element analysis technology in electrolytes, specifically relating to a fluorescent probe for detecting electrolyte viscosity, its preparation method, and its application. Background Technology

[0002] Electrolyte, as a crucial component of a battery, plays a vital role in battery operation. Viscosity, a fundamental property of the electrolyte, is highly correlated with both electrolyte and battery performance. On one hand, the Nernst-Einstein equation reveals the relationship between viscosity and particle diffusion, indicating that viscosity directly affects the transport properties of particles in the electrolyte, thus influencing battery polarization and rate performance. On the other hand, viscosity affects the wettability of the electrolyte to other battery materials, a factor that must be considered in actual production. There are various traditional methods for measuring electrolyte viscosity, commonly including rotational viscometers, cylindrical viscometers, and the pipe flow method. A rotational viscometer determines the viscosity value by measuring the torque generated when the electrolyte rotates on a rotating cylinder. A cylindrical viscometer calculates the viscosity value by measuring the flow velocity generated when the electrolyte flows inside a cylinder. The pipe flow method involves flowing the electrolyte through a pipe of a certain length and calculating the viscosity value based on the flow velocity and pressure difference. These methods suffer from cumbersome processes and complex data post-processing. Furthermore, the sensitivity and accuracy of these instruments largely depend on the operator's skill, making it difficult to guarantee accuracy. Therefore, exploring an efficient method for obtaining electrolyte viscosity to aid in the evaluation, screening, and design of electrolytes is of great significance. Small molecule organic fluorescent probes are tools that convert intermolecular interactions into optical signals and transmit them to the outside world. They have attracted considerable attention due to their high selectivity, high sensitivity, and ease of operation. Therefore, designing a fluorescent probe specifically for detecting electrolyte viscosity is of great importance.

[0003] Chinese invention patent document with publication number CN114957041A discloses a fluorescent probe for detecting the viscosity of industrial lubricating oil, its preparation method and application. The ethyl ester group on the electron donor of the probe makes the probe lipophilic, which hinders its diffusion in aqueous solution, making it difficult to use for detecting electrolyte viscosity.

[0004] Chinese invention patent document with publication number CN114957041A discloses a fluorescent probe for detecting the viscosity of beverages, its preparation method and application. The probe has good dispersibility in an aqueous environment, but its emission wavelength is relatively short and it is easily interfered with by autofluorescence, resulting in a strong background signal, which limits its use for detecting the viscosity of complex solution systems. Summary of the Invention

[0005] The purpose of this invention is to provide a fluorescent probe for detecting electrolyte viscosity, its preparation method and application. This fluorescent probe has a sensitive fluorescence response to electrolyte viscosity, can be efficiently applied to the rapid detection of electrolyte viscosity, and has a simple and quick synthesis method, making it suitable for large-scale production.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] In a first aspect, the present invention provides a fluorescent probe for detecting electrolyte viscosity, abbreviated as TV, with the structural formula shown in (Ⅰ):

[0008] R1 is one of —COOH, —CH2OH, or —CH3.

[0009] Secondly, the method for preparing the fluorescent probe for detecting electrolyte viscosity according to the present invention includes the following steps:

[0010] R1 is one of —COOH, —CH2OH, or —CH3.

[0011] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde and benzoindole derivative were dissolved in anhydrous ethanol, an organic base catalyst was added, and the mixture was heated under reflux and stirred in a nitrogen atmosphere to precipitate a solid. The solid was then filtered and dried to obtain the target product, a fluorescent probe.

[0012] Preferably, the molar ratio of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde to the benzoindole derivative is 1:1.3~1.5; the structural formula of the benzoindole derivative is:

[0013] R1 is one of —COOH, —CH2OH, or —CH3.

[0014] Preferably, the molar volume ratio of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde to anhydrous ethanol is 1 mmol: 10~15 mL.

[0015] Preferably, the organic base catalyst is N,N-diisopropylethylamine or piperidine.

[0016] Preferably, the molar volume ratio of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde to the organic base catalyst is 1 mmol: 0.05~0.1 mL.

[0017] Preferably, the temperature of the heating, reflux, and stirring reaction is 90~110℃, and the reaction time is 7~8h.

[0018] Thirdly, the present invention provides an application of the above-mentioned fluorescent probe in electrolyte viscosity detection.

[0019] Preferably, the fluorescent probe is used to detect the glycerol content in the electrolyte.

[0020] The reaction mechanism of this invention is as follows: The fluorescent probe molecule of this invention identifies viscosity through a twisted intramolecular charge transfer (TICT) mechanism. The 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde group in the fluorescent probe molecule possesses several excellent properties, such as ease of modification, good photostability, large Stokes shift, high fluorescence quantum yield, and low synthesis cost. It also possesses a relatively reactive reaction site—the aldehyde group—making it a suitable fluorophore donor for the probe. 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde is linked to a benzoindole derivative via a C / C double bond. In this structure, the C / C double bond rotates freely in low-viscosity solutions to form a twisted intramolecular charge transfer (TICT) state. This intramolecular rotation relaxes the excitation energy, quenching the fluorescence. In high-viscosity environments, the intramolecular rotation is suppressed, resulting in a strong red fluorescence signal, thus enabling viscosity detection. Furthermore, the fluorescent probe of this invention has a longer emission wavelength, is less susceptible to interference from autofluorescence, and is more suitable for application in complex solution systems. Most organic compounds containing benzene rings are poorly soluble in aqueous solutions, but the presence of some hydrophilic groups can significantly increase their solubility. The fluorescent probe of this invention contains hydroxyl and / or carboxyl hydrophilic groups, which can form hydrogen bonds with water molecules in aqueous solutions. Therefore, the fluorescent probe of this invention has good solubility in aqueous solutions. Since the electrolyte is a water-based solution, the fluorescent probe of this invention also has good solubility in the electrolyte.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The fluorescent probe of this invention has high sensitivity to viscosity, from the attached Figure 2 and attached Figure 3 It can be seen that as the viscosity increases, the fluorescence intensity increases visibly, and the fluorescence intensity has a good linear relationship with the logarithm of the viscosity, with a correlation coefficient of 0.98. (2) When detected in electrolyte, it has high selectivity and emits strong fluorescence in 90% glycerol aqueous solution. The presence of other considerable amounts of interfering substances has no significant effect on the fluorescence intensity, and the fluorescence intensity is almost the same as that of the control group. (3) The fluorescent probe of the present invention has a longer emission wavelength, is less susceptible to interference from autofluorescence, and is more suitable for application in complex solution systems; (4) The fluorescent probe TV of the present invention can be synthesized in one step, which is simple to operate and convenient and quick in post-processing. The raw materials are simple and easy to obtain, and the manufacturing cost is low. Attached Figure Description

[0022] Figure 1 This is a synthetic route diagram of the fluorescent probe of the present invention; Figure 2 The fluorescence spectrum of the fluorescent probe TV in Experiment Example 1 shows the change in fluorescence intensity as a function of solution viscosity. Figure 3 The graph shows the linear relationship between the log value of fluorescence intensity and the log value of solution viscosity in Experimental Example 1. Figure 4 This is a fluorescence intensity graph showing the selective detection of the fluorescent probe TV in Experimental Example 2; Figure 5 The image shows the fluorescence spectrum of the fluorescent probe TV in Experiment Example 3 in response to changes in electrolyte viscosity. Detailed Implementation

[0023] The specific implementation of the present invention will be further described below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0024] The synthetic route of the molecular fluorescent probe TV for electrolyte viscosity detection described in this invention is as follows: Figure 1 As shown.

[0025] Example 1 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and benzoindole derivative (R1 is -COOH, 2.6 mmol) were dissolved in anhydrous ethanol (20 mL), and 0.1 mL of N,N-diisopropylethylamine was added. The mixture was heated to 90 °C under a nitrogen atmosphere and then refluxed with stirring for 8 h. A reddish-purple solid precipitated, which was then filtered and dried to obtain the fluorescent probe TV.

[0026] Characterized by proton nuclear magnetic resonance spectroscopy: 1 H NMR (300 MHz, DMSO- d 6) δ 10.38 (s,1H), 8.02 (d,J = 14.7Hz, 2H), 7.95 (d,J = 7.6 Hz, 1H),7.58 (t,J = 15.4Hz,1H),7.51 (d,J = 7.4 Hz, 1H),7.45 –7.38 (m, 2H),7.15 (d, J = 7.7 Hz, 1H), 6.77(dd, J = 12.7 Hz, 2H),6.54 (d, J = 8.7 Hz, 1H),6.33 (d, J = 7.6 Hz, 1H),4.3(t, J = 2.4 Hz, 2H), 2.53 (t, J = 7.1 Hz, 2H), 1.44 (s, 6H). Further validation was performed using high-resolution mass spectrometry: HR-MS (ESI): theoretically calculated molecular mass-to-charge ratio [C 24 H 22 NO5 + +H] + The actual molecular mass-to-charge ratio is 455.1683, and the product synthesized in this embodiment can be determined to be the fluorescent probe TV through proton and mass spectrometry data. Its structural formula is as follows: Example 2

[0027] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and a benzoindole derivative (R1 is -COOH, 2.8 mmol) were dissolved in anhydrous ethanol (25 mL), and 0.15 mL of N,N-diisopropylethylamine was added. The mixture was heated to 100 °C under a nitrogen atmosphere and then refluxed with stirring for 7.5 h. A reddish-purple solid precipitated, which was then filtered and dried to obtain the fluorescent probe TV.

[0028] The characterization results of the fluorescent probe TV obtained in this embodiment are the same as those in Implementation Case 1. Example 3

[0029] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and benzoindole derivative (R1 is -COOH, 3 mmol) were dissolved in anhydrous ethanol (30 mL), 0.2 mL of piperidine was added, and the mixture was heated to 110 °C under a nitrogen atmosphere and then refluxed and stirred for 7 h. A reddish-purple solid was precipitated, filtered, and dried to obtain the fluorescent probe TV.

[0030] The characterization results of the fluorescent probe TV obtained in this embodiment are the same as those in Implementation Case 1. Example 4

[0031] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and a benzoindole derivative (R1 is -CH2OH, 2.6 mmol) were dissolved in anhydrous ethanol (20 mL), and 0.1 mL of N,N-diisopropylethylamine was added. The mixture was heated to 90 °C under a nitrogen atmosphere and then refluxed with stirring for 8 h. A reddish-purple solid precipitated, which was then filtered and dried to obtain the fluorescent probe TV.

[0032] Example 5

[0033] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and benzoindole derivative (R1 is -CH2OH, 3 mmol) were dissolved in anhydrous ethanol (30 mL), 0.2 mL of piperidine was added, and the mixture was heated to 110 °C under a nitrogen atmosphere and then refluxed and stirred for 7 h. A reddish-purple solid was precipitated, filtered, and dried to obtain the fluorescent probe TV.

[0034] The characterization results of the fluorescent probe TV obtained in this embodiment are the same as those in implementation case 4. Example 6

[0035] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and benzoindole derivative (R1 is -CH3, 2.6 mmol) were dissolved in anhydrous ethanol (20 mL), and 0.1 mL of N,N-diisopropylethylamine was added. The mixture was heated to 90 °C under a nitrogen atmosphere and then refluxed with stirring for 8 h. A reddish-purple solid precipitated, which was then filtered and dried to obtain the fluorescent probe TV.

[0036] Example 7

[0037] 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde (2 mmol) and benzoindole derivative (R1 is -CH3, 3 mmol) were dissolved in anhydrous ethanol (30 mL), 0.2 mL of piperidine was added, and the mixture was heated to 110 °C under a nitrogen atmosphere and then refluxed and stirred for 7 h. A reddish-purple solid was precipitated, filtered, and dried to obtain the fluorescent probe TV.

[0038] The characterization results of the fluorescent probe TV obtained in this embodiment are the same as those in implementation case 6.

[0039] Experimental Example 1

[0040] The response of fluorescent probe TV to viscosity in aqueous solution The fluorescent probe TV prepared in Example 1 was dissolved in dimethyl sulfoxide to prepare a probe stock solution with a concentration of 10 mM. During testing, the concentration of the fluorescent probe TV was maintained at 10 μM in different mass ratios of glycerol / water. Test systems with different mass ratios of glycerol and water were prepared, with glycerol mass percentages of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%. The viscosities of these nine test systems at room temperature were 0.94 CP, 1.19 CP, 1.61 CP, 2.43 CP, 3.8 CP, 6.44 CP, 12.2 CP, 27.4 CP, and 79.67 CP, respectively. Maintaining a total test volume of 5 mL, and using a wavelength of 475 nm as the excitation wavelength, the fluorescence intensity as a function of viscosity was measured as shown in the following figure. Figure 2 As shown, the linear response to viscosity is as follows: Figure 3 As shown. From Figure 2 It can be seen that as the solution viscosity gradually increases, the fluorescence intensity of the probe at 632 nm also increases; simultaneously, from Figure 3 As can be seen, the logarithmic value of its fluorescence intensity and the logarithmic value of the solution viscosity show a good linear relationship (R0). 2 =0.98), demonstrating that the fluorescent probe provided by this invention has good sensitivity to viscosity. From Figure 2 As can be seen, the fluorescence intensity of the probe at 632 nm increases as the solution viscosity gradually increases. The test results show that the fluorescent probe of this invention has a good response to viscosity and can characterize changes in viscosity by varying fluorescence intensity, making it suitable for detecting electrolyte viscosity, and particularly suitable for detecting the glycerol content in electrolytes.

[0041] Experimental Example 2

[0042] Selectivity test of fluorescent probe TV The fluorescent probe TV prepared in Example 1 was dissolved in dimethyl sulfoxide to prepare a probe stock solution with a probe concentration of 10 mM. Based on the analysis of the electrolyte components, the analyte was identified as Na. + K + Al 3+ Fe 3+ Ni + VO 2 + V 5+ P, SiO2, etc. are used as interfering elements to obtain the corresponding mother liquor of interfering elements for later use.

[0043] 5 μL of the probe stock solution was added to 5 mL of 90% glycerol / water and a solution containing 100 equivalents of each interfering element, respectively, to prepare test solutions with a fluorescent probe concentration of 10 μM and a analyte concentration of 1000 μM. The fluorescence intensity of each group of test samples at 632 nm was measured, and a bar chart of the test results was plotted. The results are shown below. Figure 4 As shown. From Figure 4 As can be seen, the fluorescence intensity of the fluorescent probe TV did not change significantly in the presence of various interfering elements. Only in a 90% glycerol / water solution was a significant increase in fluorescence intensity observed, indicating that the fluorescent probe TV has good selective response to viscosity; only changes in viscosity cause changes in fluorescence intensity. Furthermore, this fluorescent probe exhibits high chemical stability and inertness to various impurity elements in the electrolyte. Therefore, it can be proven that the probe TV has unique viscosity detection capabilities and can achieve the detection of electrolyte viscosity.

[0044] Experimental Example 3

[0045] The response of fluorescent probe TV to viscosity in electrolyte Adding an appropriate amount of glycerol to the freshly prepared electrolyte can change its viscosity, thereby improving its stability and conductivity. However, if the viscosity is too high, it will affect the fluidity of the electrolyte, limit the migration speed of ions, and reduce conductivity. Furthermore, it will cause blockage of the pores in the electrolysis equipment. Therefore, the detection of its viscosity is of great significance.

[0046] The fluorescent probe TV prepared in Example 1 was dissolved in dimethyl sulfoxide to prepare a probe stock solution with a concentration of 10 mM. During testing, the concentration of the fluorescent probe TV was maintained at 10 μM in different mass ratios of glycerol / electrolyte. Test systems with different mass ratios of glycerol and electrolyte were prepared, with glycerol mass percentages of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%. The total test volume was maintained at 5 mL, and the excitation wavelength was 475 nm. The fluorescence intensity as a function of viscosity was measured as shown in the following figure. Figure 5 As shown. From Figure 5 As can be seen, the fluorescence intensity of the probe at 632 nm significantly increases as the solution viscosity gradually increases. The test results further demonstrate that this fluorescent probe can be applied to electrolyte solutions with complex solvent systems and can sensitively respond to changes in electrolyte viscosity.

[0047] Test Example 4

[0048] The response of the fluorescent probes prepared in Examples 4 and 6 to viscosity is shown in Table 1.

[0049]

Claims

1. A fluorescent probe for detecting electrolyte viscosity, characterized in that, Its structural formula is: ,(I), R1 is either -COOH or -CH2OH.

2. A method for preparing a fluorescent probe for detecting electrolyte viscosity as described in claim 1, characterized in that, The synthesis route is as follows: ； R1 is either -COOH or -CH2OH; 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde and benzoindole derivative were dissolved in anhydrous ethanol, an organic base catalyst was added, and the mixture was heated under reflux and stirred in a nitrogen atmosphere to precipitate a solid. The solid was then filtered and dried to obtain the target product, a fluorescent probe.

3. The method for preparing a fluorescent probe for detecting electrolyte viscosity according to claim 2, characterized in that, The molar ratio of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde to the benzoindole derivative is 1:1.3-1.5; the structural formula of the benzoindole derivative is: R1 is either -COOH or -CH2OH.

4. The method for preparing a fluorescent probe for detecting electrolyte viscosity according to claim 2, characterized in that, The molar volume ratio of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde to anhydrous ethanol is 1 mmol: 10~15 mL.

5. The method for preparing a fluorescent probe for detecting electrolyte viscosity according to claim 2, characterized in that, The organic base catalyst is N,N-diisopropylethylamine or piperidine.

6. The method for preparing a fluorescent probe for detecting electrolyte viscosity according to claim 2, characterized in that, The molar volume ratio of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxaldehyde to the organic base catalyst is 1 mmol: 0.05~0.1 mL.

7. The method for preparing a fluorescent probe for detecting electrolyte viscosity according to claim 2, characterized in that, The temperature of the heating, reflux, and stirring reaction is 90~110℃, and the reaction time is 7~8h.

8. The application of a fluorescent probe for detecting electrolyte viscosity as described in claim 1 in the detection of electrolyte viscosity, characterized in that, The fluorescent probe is used to detect the glycerol content in the electrolyte.

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