Aluminum ion complex for detecting trace water, preparation method and application of fluorescence sensor

Abstract

The invention provides an aluminum ion complex for detecting trace water, a preparation method of the aluminum ion complex and application of a fluorescence sensor, and belongs to the technical field of fluorescence sensors. According to the invention, pyridine-2-formaldehyde and benzoyl hydrazine are subjected to a one-step reaction to synthesize a ligand, the ligand is complexed with aluminum ions to prepare the aluminum ion complex capable of detecting trace water, the preparation method is simple, the raw materials are low in price, and the complex is good in stability. The complex can be used as a fluorescence sensor to show better responsiveness and higher sensitivity to water, the detection process is simple and rapid, and visual qualitative detection can be performed on water; the moisture in the food can be quantitatively detected by utilizing a good linear relationship between the fluorescence emission intensity and the water content. Therefore, the complex prepared by the invention has potential application prospects in the aspect of quantitative analysis of water.

Description

Technical Field

[0001] This invention belongs to the field of fluorescence sensor technology. Background Technology

[0002] Water is a vital natural resource for daily life and industrial production, but in certain situations (such as chemical processes and the food industry), even trace amounts of water are considered common impurities or contaminants. In chemical synthesis reactions, water content must be strictly controlled because it can affect the chemical properties and activity of raw materials, reducing product yield. For example, trace amounts of water in organometallic reactions can reduce or even quench the reactivity of organometallic compounds, decreasing product yield and potentially causing serious safety accidents such as fires and explosions. Excessive moisture in pharmaceuticals can affect the physiological activity and chemical stability of drug components, and also impact the taste and shelf life of food. Furthermore, trace water is a deadly impurity in fuels, causing fuel line blockage and severe mechanical damage. Therefore, the sensitive quantitative detection of trace water has become a field of great interest.

[0003] Traditional analytical techniques such as Karl Fischer titration, chromatography-mass spectrometry, and electrochemical methods can be used to determine moisture in common organic solvents. However, these methods suffer from drawbacks such as cumbersome operation, expensive equipment, stringent sample preparation requirements, and the use of toxic reagents (such as SO2, I2, and pyridine). In contrast, fluorescence sensors based on fluorescence and colorimetry have attracted much attention due to their advantages such as good selectivity, high sensitivity, simple operation, low cost, and fast detection speed, and are gradually becoming the preferred method for detecting water content. Although many fluorescence sensors have been reported for qualitative and quantitative detection of trace amounts of water in the environment or food, these methods still suffer from drawbacks such as long response times, complex material preparation, and low sensitivity. Summary of the Invention

[0004] The purpose of this invention is to overcome the drawbacks of existing technologies, such as long detection time, high cost, and complex synthesis, and to provide a low-cost, simple-process, and high-yield trace water fluorescence sensor. To achieve the above objective, this invention adopts the following technical solution:

[0005] An aluminum ion complex for detecting trace amounts of water is formed by complexing aluminum ions with a small molecule organic compound (NSP) as a ligand. The IUPAC name of the small molecule organic compound (NSP) is N'-(2-pyridyl)methylenebenzoylhydrazide, and its structural formula is as follows:

[0006]

[0007] The generated complex NSP@Al 3+ The structure is as follows:

[0008]

[0009] Wherein, X represents the anion that forms a soluble aluminum salt with aluminum ions, preferably perchlorate ions;

[0010] The preparation method of the aluminum ion complex for detecting trace amounts of water includes the following steps:

[0011] 1) Preparation of small molecule organic compounds (NSP):

[0012] Pyridine-2-carboxaldehyde and benzoylhydrazine in a molar ratio of 1:(0.8~1.2) were dissolved in anhydrous ethanol, heated to reflux, reacted for 2~5 hours, cooled to room temperature, poured into ice water, filtered, and dried under vacuum to obtain a white solid, which is the small molecule organic compound NSP.

[0013] 2) Complex NSP@Al 3+ Preparation:

[0014] NSP and Al 3+ The NSP@Al was dissolved and mixed in anhydrous acetonitrile at a molar ratio of 1:(0.9~1.1), and then diluted with anhydrous acetonitrile to obtain NSP@Al. 3+ Complex solution.

[0015] In step 2), the preferred molar ratio is 1:1.

[0016] This invention also provides the application of the aforementioned fluorescent sensor for detecting trace amounts of water using aluminum ion complexes, specifically the following method:

[0017] 1) Prepare M (M≥2) portions of NSP@Al 3+ For the complex solution, add M parts of water at different volume ratios, ranging from 0% to 3.33% by volume, and dilute with anhydrous acetonitrile to the required test solution. The required solution contains NSP@Al. 3+ The concentration was 50 μmol / L; fluorescence spectroscopy was performed on the above M group solutions, and the fluorescence emission spectra of the M group solutions were measured under 333 nm excitation; based on the fluorescence emission spectra, calibration curves between the fluorescence intensity of the series of solutions and the corresponding water volume ratio were plotted.

[0018] 2) Select the samples to be tested, soak them in anhydrous acetonitrile for half an hour, centrifuge them, take the supernatant and add it to the solution required for testing, transfer the resulting mixed solution to a fluorescence spectrophotometer, set the excitation wavelength to 333 nm, perform fluorescence spectrum scanning, record the fluorescence intensity at the maximum emission wavelength, and calculate the water content in the sample to be tested according to the calibration curve.

[0019] Furthermore, using the standard addition method, a known volume of water was added to the supernatant of the above sample, and after mixing thoroughly, its fluorescence spectrum was tested, the fluorescence intensity was recorded, and the total water content and recovery rate in the sample were calculated.

[0020] The beneficial effects of this invention are as follows: the aluminum ion complex prepared by the method of this invention can effectively detect the water content. It has the advantages of simple preparation, easy operation, low raw material price, rapid response and high detection sensitivity. It can perform visual qualitative detection of water content and has broad application prospects. Attached Figure Description

[0021] Figure 1 The 1H NMR spectrum of the ligand compound NSP;

[0022] Figure 2 This is the selective fluorescence emission spectrum of NSP for metal ions;

[0023] Figure 3 The selective fluorescence colorimetric diagram of NSP for metal ions (365 nm illumination);

[0024] Figure 4 Job's analysis chromatogram of NSP and aluminum ions;

[0025] Figure 5 For the preparation of NSP@Al 3+ ESI-MS image of the coordination compound;

[0026] Figure 6 For Al 3+ Coordination mechanism diagram with NSP;

[0027] Figure 7 For NSP@Al 3+ UV-Vis absorption spectrum of the complex in response to water;

[0028] Figure 8 For NSP@Al 3+ Fluorescence spectrum of the complex in response to water;

[0029] Figure 9 For different water contents, NSP@Al 3+ The effect of complex fluorescence spectra;

[0030] Figure 10 For NSP@Al 3+ Standard curve of complex composition versus water content;

[0031] Figure 11 The fitted Stern-Volmer curve;

[0032] Figure 12 For NSP@Al 3+ Fluorescence spectra of the complexes for detection in actual samples. Detailed Implementation

[0033] To make the objectives, technical solutions, and effects of the present invention clearer, the specific embodiments of the present invention are described below in conjunction with the accompanying drawings.

[0034] Example 1 [Preparation of Ligand Compound (NSP)]

[0035] The synthetic route of the ligand compound (NSP) in this embodiment is as follows:

[0036]

[0037] The specific steps of its preparation process are as follows:

[0038] In a 100 mL single-necked round-bottom flask, 408.5 mg (3.3 mmol) of benzoyl hydrazide and 0.29 mL of pyridine-2-carboxaldehyde (3.1 mmol) were accurately weighed using an electronic analytical balance and added to 25 mL of anhydrous ethanol. The mixture was refluxed and stirred in an oil bath at 80 °C for 3 hours. After cooling to room temperature, the solution was poured into 100 mL of ice water, resulting in a large amount of white solid. The mixture was filtered, and the filter cake was washed three times with water. After vacuum drying, 601.3 mg of white solid product was obtained, with a yield of 89%.

[0039] The molecular structural formula of the obtained white solid is:

[0040]

[0041] 1 H NMR (400 MHz, d6-DMSO) δ: 10.46 (s, 1H), 8.61 (d, J = 4.4 Hz, 1H), 8.33 (s, 1H), 8.01 (d, J = 7.6 Hz, 1H), 7.91 (d, J = 7.6 Hz, 2H), 7.82 (t, J = 7.6 Hz, 1H), 7.61 (t, J = 7.6 Hz, 1H), 7.53 (t, J = 7.6 Hz, 2H), 7.36 (t, J = 6.0 Hz, 1H).

[0042] Example 2 [Selectivity of Metal Ions by Ligand Compounds (NSP)]

[0043] Accurately weigh 2.3 mg of NSP using an analytical balance with a concentration of 0.01 g / mL, dissolve it in 1 mL of anhydrous acetonitrile, and prepare a ligand compound with a concentration of 1 × 10⁻⁶ mg / mL. -2 mol / L acetonitrile stock solution.

[0044] Sixteen metal ions were selected, namely Na+, ... + Al 3+ Ca2+ Cd 2+ Fe 2+ Co 2+ K + Mg 2+ Ni 2+ Cu 2+ Pb 2 + Fe 3+ 、Tb 3+ Zn 2+ Mn 2+ and Er 3+ These metal ions are all in perchlorate form. A certain mass of each metal salt was accurately weighed using a 0.01 g electronic analytical balance, dissolved in 1 mL of anhydrous acetonitrile, and prepared to a metal ion concentration of 1 × 10⁻⁶. -2 A solution of mol / L.

[0045] Accurately transfer 15 μL of each of the 17 acetonitrile stock solutions of the ligand compounds into centrifuge tubes. One of these is a blank solution, and the others are each diluted with 5 times their volume of metal ion acetonitrile solution to a final volume of 3 mL with anhydrous acetonitrile to prepare the test solutions. Irradiate the prepared solutions with 365 nm ultraviolet light. Figure 2 As shown, add Al 3+ The solution emitted a bright blue fluorescence, while the addition of other metal ion solutions did not produce fluorescence, indicating that the ligand is effective against Al. 3+ It exhibits good selectivity.

[0046] Fluorescence spectroscopy determination: The prepared solutions were sequentially transferred to cuvettes with an optical path length of 1 cm, and fluorescence emission spectra were measured on an LS-55 fluorescence spectrophotometer with an excitation wavelength of 333 nm. The results are as follows: Figure 3 As shown. Only with the addition of Al 3+ In the solution system, the fluorescence intensity at 442 nm was significantly enhanced, while the fluorescence intensity in solutions with other metal ions was very weak, indicating that the ligands significantly enhanced the fluorescence intensity of Al. 3+ It demonstrates excellent selective recognition capabilities.

[0047] Example 3 [Ligand compound (NSP) and Al] 3+ Combination Mode

[0048] Take 10 centrifuge tubes and accurately transfer the NSP and Al obtained in Example 2. 3+ Stock solution (concentration of 1×10) -2 The NSP and Al were mixed (1 mol / L) and diluted to 3 mL with anhydrous acetonitrile to make a total concentration of 50 μmol / L. 3+The molar ratios were 10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8 and 1:9, respectively. The prepared solutions were tested for fluorescence emission spectra with an excitation wavelength of 333 nm and then subjected to Job's analysis.

[0049] like Figure 4 As shown, with Al 3+ As the molar ratio increases, the fluorescence intensity at 442 nm gradually increases. When Al... 3+ The molar percentage is 50% ([Al) 3+ ] / [NSP + Al 3+ When [equation] = 0.5, the system reaches its maximum emission intensity at 442 nm, indicating that the ligand and Al [equation] [are effective]. 3+ Coordination was performed in a 1:1 molar ratio mode.

[0050] To further verify NSP and Al 3+ The optimal coordination mode, determined by ESI-MS for NSP and Al 3+ The mixed solution was analyzed. For example... Figure 5 As shown, an ion peak ([NSP+Al)) was detected at a mass-to-charge ratio (m / z) of 449.9687. 3+ +2ClO4 - ] + The theoretical value is 449.9688. This experiment demonstrates that NSP and Al 3+ Stable aluminum ion complexes are formed in a 1:1 molar ratio (e.g.) Figure 6 ).

[0051] Example 4 [NSP@Al] 3+ Applications of complexes in the detection of water content

[0052] Accurately weigh 2.3 mg NSP and 4.9 mg aluminum perchlorate into a centrifuge tube using a 0.01 g electronic analytical balance. Dissolve them in 1 mL of anhydrous acetonitrile. At this point, the NSP and Al in the solution will be... 3+ A complex was formed at a molar ratio of 1:1, yielding a concentration of 1×10⁻⁶. -2 mol / L NSP@Al 3+ Complex solution. The prepared NSP@Al 3+ The complex solution was used as a stock solution for subsequent tests.

[0053] Test Experiment 1, NSP@AI 3+ The responsiveness of coordination compounds to water

[0054] Accurately transfer the above NSP@Al 3+15 μL of the complex stock solution was added to a centrifuge tube, followed by 100 μL of pure water. The solution was then diluted to 3 mL with anhydrous acetonitrile. The UV-Vis absorption and fluorescence emission spectra of the prepared solution were then measured. The results are as follows: Figure 7 As shown, after adding a trace amount of water, NSP@Al 3+ The absorption peak of the complex at 333 nm shifted to 300 nm, and its spectral shape was similar to that of the NSP-only complex. It should be noted that after the addition of water, the absorption spectrum did not completely revert to the NSP-only form, presumably due to a shift in the absorption spectrum caused by the presence of water.

[0055] In fluorescence spectroscopy testing, NSP@Al 3+ The fluorescence spectrum and emission intensity of the complex also revert to the state of the neutral ligand in the presence of water. Figure 8 Under 365 nm ultraviolet light illumination, the emission color clearly changed from bright blue to dark, which is observable to the naked eye. These spectral results indicate that NSP@Al 3+ The complex underwent a reversible hydrolysis reaction in the presence of water.

[0056] Furthermore, the complex responds to water within 10 seconds, indicating that NSP@Al 3+ Complexes provide a rapid and convenient fluorescence detection platform.

[0057] Test Experiment 2, NSP@Al 3+ Sensitivity of coordination compounds for water detection

[0058] Accurately transfer 15 portions of NSP@Al prepared by the above method. 3+ 15 μL of the complex stock solution was added to different volumes of pure water, with the water volume gradually increasing from 0 μL to 25 μL. The solution was then diluted to 3 mL with anhydrous acetonitrile. The NSP concentration was 50 μmol / L, and the water volume percentage gradually increased from 0% to 0.83%. The fluorescence spectra of the 15 solutions were then tested sequentially, with an excitation wavelength of 333 nm.

[0059] The results are as follows Figure 9 As shown, the fluorescence intensity at 442 nm gradually decreases with increasing water content. This phenomenon may be due to the fact that NSP@Al... 3+ The complex undergoes partial or complete hydrolysis. At low water contents (0-0.3 v / v%), the fluorescence intensity at 442 nm decreases linearly. Figure 10 The linear equation is y = -1245.6 [H2O] + 227.5, with a correlation coefficient of 0.9926. According to the formula, NSP@Al 3+The detection limit of the complex for water was 0.0042% (v / v), indicating that the prepared NSP@Al 3+ Complexes can be used for the quantitative detection of water.

[0060] Similarly, the linear relationship between the ratio of fluorescence intensity changes at 442 nm and the water volume ratio was fitted, such as... Figure 11 As shown, through fitting, the relationship between the fluorescence intensity change ratio and the water volume ratio was obtained: F0 / F = 11519 [H2O] + 0.99, where F0 and F represent the fluorescence intensity at 442 nm before and after adding water, respectively, and the linear slope represents the quenching constant K. sv = 1.15×10 4 M -1 With an intercept b = 0.99, the results indicate that water has a high affinity for NSP+Al. 3+ The complex has a high quenching efficiency.

[0061] Furthermore, during the experiment, as the water content increased, NSP@Al 3+ The fluorescence emission color of the complex solution under 365 nm ultraviolet light gradually changes from bright blue to dark, and this phenomenon can serve as an important basis for estimating water content.

[0062] Test Experiment 3, NSP@Al 3+ Complexation testing for water content in food

[0063] Weigh 2.0 g each of honey, baking soda, white sugar, and flour, and place them separately in 10 mL glass vials. Add 5 mL of acetonitrile to each vial and stir at room temperature for 20 minutes. Centrifuge the sample solutions to obtain the supernatant. Accurately transfer 15 μL of the NSP@Al prepared by the above method. 3+ The complex stock solution was placed in a quartz cuvette and diluted to 3 mL with the prepared sample supernatant to obtain the sample. The fluorescence emission spectrum of the sample solution was measured with 333 nm as the excitation wavelength, and the fluorescence intensity at the maximum emission wavelength of 442 nm was recorded. The water content in the actual sample was calculated based on the fitted standard curve and the established linear relationship equation.

[0064] The measurement results are as follows Figure 12 As shown, the fluorescence intensity of each sample solution at 442 nm is relative to that of NSP@Al alone. 3+ The concentrations of all complexes decreased. Based on the linear relationship obtained from the fluorescence sensitivity experiment, the water content of honey, baking soda, white sugar, and flour were calculated to be 0.317%, 0.131%, 0.288%, and 0.042%, respectively.

[0065] Simultaneously, standard volumes of water were added to the samples, and the solutions were diluted to 5 mL with anhydrous acetonitrile using the same method described above. The volume percentage of water added was 0.02%. After centrifugation, 15 μL of the NSP@Al prepared by the above method was used as a supernatant. 3+ The stock solution of the complex was diluted to 3 mL, and the fluorescence emission spectrum of the sample solution was measured using 333 nm as the excitation wavelength. The calculated recovery rate of the sample solution was 93%-110%. These results indicate that the quantitative analysis method of this invention is not affected by other components in the sample; that is, the above results all conform to the guidelines for the validation of quantitative analysis methods. The prepared NSP@Al 3+ The complex can serve as an effective fluorescent sensor for the quantitative detection of water content.

[0066] The above description is merely a preferred embodiment of the present invention, and is described in detail and specifically, but it is not intended to limit the present invention. For those skilled in the art, any changes or improvements can be made based on the above embodiments, and all such changes or improvements should be included within the protection scope of the present invention.

Claims

1. An aluminum ion complex for detecting trace amounts of water, characterized in that, This complex is formed by complexing aluminum ions with a small molecule organic compound NSP as a ligand. The IUPAC name of NSP is N'-(2-pyridyl)methylenebenzoylhydrazide, and its structural formula is as follows: The generated complex NSP@Al 3+ The structure is as follows: Where X represents the anion that forms a soluble aluminum salt with aluminum ions.

2. The aluminum ion complex for detecting trace amounts of water according to claim 1, characterized in that, Anion X is a perchlorate ion.

3. The method for preparing aluminum ion complexes for detecting trace amounts of water as described in claim 1, characterized in that, The steps of this method are as follows: 1) Preparation of the small molecule organic compound NSP: Pyridine-2-carboxaldehyde and benzoylhydrazine in a molar ratio of 1:(0.8~1.2) were dissolved in anhydrous ethanol, heated to reflux, reacted for 2~5 hours, cooled to room temperature, poured into ice water, filtered, and dried under vacuum to obtain a white solid, which is the small molecule organic compound NSP. 2) Complex NSP@Al 3+ Preparation: Small molecule organic compounds NSP and Al 3+ The NSP@Al was dissolved and mixed in anhydrous acetonitrile at a molar ratio of 1:(0.9~1.1), and then diluted with anhydrous acetonitrile to obtain NSP@Al. 3+ Complex solution.

4. The method for preparing aluminum ion complexes for detecting trace amounts of water according to claim 3, characterized in that, In step 2), the molar ratio is 1:

1.

5. Use of the fluorescent sensor for detecting trace amounts of water using aluminum ion complexes as described in claim 1.

6. The application of the fluorescence sensor according to claim 5, characterized in that, The specific method is as follows: 1) Prepare M (M≥2) portions of NSP@Al 3+ For the complex solution, add M parts of water at different volume ratios, ranging from 0% to 3.33% by volume, and dilute with anhydrous acetonitrile to the required test solution. The required solution contains NSP@Al. 3+ The concentration was 50 μmol / L; fluorescence spectroscopy was performed on the above M group solutions, and the fluorescence emission spectra of the M group solutions were measured under 333 nm excitation. Based on the fluorescence emission spectra, a series of calibration curves were plotted between the fluorescence intensity of the solutions and the corresponding water volume ratios. 2) Select the samples to be tested, soak them in anhydrous acetonitrile for half an hour, centrifuge them, take the supernatant and add it to the solution required for testing, transfer the resulting mixed solution to a fluorescence spectrophotometer, set the excitation wavelength to 333 nm, perform fluorescence spectrum scanning, record the fluorescence intensity at the maximum emission wavelength, and calculate the water content in the sample to be tested according to the calibration curve.

7. The application of the fluorescence sensor according to claim 6, characterized in that, Using the standard addition method, a known volume of water was added to the sample supernatant in step 2), and after mixing thoroughly, its fluorescence spectrum was tested, the fluorescence intensity was recorded, and the total water content and recovery rate in the sample were calculated.

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