A fluorescent sensitive membrane for detecting mercury ions in water and a preparation method thereof

Abstract

This invention discloses a fluorescent sensitive membrane for detecting mercury ions in water and its preparation method. The sensitive membrane comprises a fluorescent probe and a physically cross-linked matrix. The fluorescent probe is prepared using 7-(diethylamino)coumarin-3-carboxaldehyde, 3-methyl-2-benzothiazolidinone hydrazone hydrochloride, and ethanol. Chitosan, glycerol, and acetic acid solutions are then added to a round-bottom flask and stirred until the chitosan is completely dissolved. Next, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride is added, and stirring continues at room temperature to obtain a clear and transparent solution. The fluorescent probe is then added, and stirring continues. Finally, the solution is poured into a glass dish to evaporate the solvent, yielding the mercury ion detection solution. 2+ A fluorescently sensitive membrane. This membrane is sensitive to Hg in water. 2+ It has a detection function, requires no sample preparation during detection, and has the advantages of simple detection method and high detection efficiency.

Description

Technical Field

[0001] This invention belongs to the field of thin-film sensitive materials and heavy metal detection technology, and relates to a fluorescent sensitive membrane for detecting mercury ions in water and its preparation method. Background Technology

[0002] Heavy metal pollution is one of the major problems of groundwater pollution. Mercury (Hg) is one of the most toxic heavy metal elements in the environment. 2+ The main sources of pollution are industrial pollution, gold mining and smelting, coal combustion pollution, and acid rain pollution. Hg in water... 2+ Not only does it harm ecosystems, but it can also enter the human body through the ingestion of contaminated water and food or the inhalation of fumes, triggering a range of neurological disorders and posing a significant threat to human health. Therefore, there is an urgent need to develop a suitable technology for controlling Hg in groundwater. 2+ Sensitive on-site monitoring should be conducted to avoid any impact on human health.

[0003] Traditional Hg 2+ Detection methods include atomic absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), gas chromatography, high-performance liquid chromatography (HPLC), and capillary electrophoresis (CE). These methods offer advantages such as high specificity and mature instruments; however, their complexity, high cost, and difficult pretreatment processes limit their ability to achieve rapid and sensitive detection. Therefore, fluorescence sensors have been widely used in recent years. Traditional detection methods often utilize small organic molecule fluorescent probes, but these methods may cause secondary pollution to water bodies, and post-processing is complex, posing significant challenges in practical applications. Therefore, we urgently need a new material with outstanding performance to address these issues. Summary of the Invention

[0004] Regarding the above existing Hg 2+ To address the shortcomings of fluorescence sensors, this invention discloses a method for detecting heavy metal ions (Hg). 2+ The sensitive membrane used for detection is CBH / ACG, which is stable in water and can detect Hg by fluorescence method. 2+ Unaffected by interference from other ions, it possesses high sensitivity and a low detection limit, making it a promising candidate for detecting Hg in groundwater. 2+ In-situ detection.

[0005] I. Preparation of CBH / ACG Sensitive Membrane

[0006] 1) 7-(diethylamino)coumarin-3-carboxaldehyde and 3-methyl-2-benzothiazolidinone hydrochloride were co-dissolved in hot ethanol and reacted at 80-90℃ for 4-6 h under the catalysis of acetic acid. The mixture was filtered to obtain a red crude product, which was then washed three times with ethanol to obtain the fluorescent probe CBH.

[0007] The molar ratio of 7-(diethylamino)coumarin-3-carboxaldehyde to 3-methyl-2-benzothiazolidinone hydrazone hydrochloride is (1~3):1. Hot ethanol at 40~50℃ is used to aid dissolution.

[0008] 2) Chitosan and glycerol were co-dissolved in 1% acetic acid solution and stirred until the chitosan was completely dissolved. Then 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride was added and prepolymerized at room temperature for 6-8 h to obtain chitosan-based film solution.

[0009] The mass ratio of chitosan to glycerol is 1:(2~4), and the mass ratio of chitosan to 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride is (6~8):1.

[0010] 3) Add the fluorescent probe CBH to the chitosan-based membrane solution and continue stirring for 10-12 h. Then pour the solution into a glass dish to evaporate and rinse to obtain the CBH / ACG membrane.

[0011] The concentration of the fluorescent probe CBH in the chitosan-based membrane solution was 0.3~0.9 g / L.

[0012] II. Structural Characterization and Performance Evaluation of CBH / ACG Sensing Membrane

[0013] 1. Microstructure

[0014] Figure 3 This is a scanning electron microscope (SEM) image of the ACG thin film prepared by the method of this invention. Figure 4 This is a scanning electron microscope (SEM) image of the CBH / ACG thin film prepared by the method of this invention. Figure 3 and 4 The comparison shows that the surface of the CBH / ACG film is smoother and denser than that of the ACG film, indicating that the CBH fluorescent probe is stably loaded on the ACG film, providing a reliable basis for the further functionalization of chitosan films.

[0015] 2. Determination of the detection limit of mercury ions

[0016] Cut the CBH / ACG film into circular pieces with a diameter of 1 cm. Place 20 mL of deionized water in a beaker, immerse the film pieces in the water for 2–5 minutes, then remove them. First, blot the surface of the film pieces dry with filter paper. Then, add 40 μL of deionized water to the film pieces to ensure consistent water content during the test. Press the film pieces firmly onto the glass slide with a quartz plate and measure the initial fluorescence intensity of the film pieces using a fluorescence spectrophotometer. Subsequently, remove the film pieces, blot the surface dry with filter paper, and add 1 μL of Hg-containing solution to the test solution.2+ A solution of ions (concentration of 100 ppm) was thoroughly mixed to obtain a 5 ppb test solution. The thin film was then immersed in 20 mL of this solution for 2–5 minutes. After immersion, the film was blotted dry with filter paper, and then 40 μL of the solution was added to ensure consistent water content throughout the test. The film was then pressed firmly with another quartz plate, and the fluorescence intensity change was detected using a fluorescence spectrophotometer. The detection methods for other test solutions with concentrations of 10 ppb, 15 ppb, 20 ppb, 25 ppb, 30 ppb, 35 ppb, 40 ppb, 45 ppb, 50 ppb, 60 ppb, 70 ppb, and 80 ppb were the same as those for the 5 ppb solution. Finally, the results were obtained. Figure 5 The corresponding concentration-fluorescence intensity standard working curve is shown below.

[0017] from Figure 5 The corresponding concentration-fluorescence intensity standard curves shown indicate that as the concentration of Hg in the test solution increases... 2+ As the ion concentration increases, the fluorescence intensity of the sensitive membrane also gradually increases. When Hg 2+ When the ion concentration is 5 ppb, it contains Hg. 2+ The fluorescence intensity of the ion-sensitive membrane was significantly higher than that of the blank membrane, and through... Figure 6 The detection limit was calculated to be 3.6 ppb.

[0018] 3. Mercury ion selectivity and anti-interference properties

[0019] First, prepare the following solutions:

[0020] 20 mL of Hg with a concentration of 80 ppb 2+ Solution;

[0021] Each of the following solutions contains 20 mL of other metal ions with a concentration of 1000 ppb: KCl solution, MgCl2 solution, CrCl3·3H2O solution, ZnCl2 solution, FeCl3 solution, CuCl2·2H2O solution, CaCl2 solution, HgCl2 solution, PbCl2 solution, K2Cr2O7 solution, MnCl2·4H2O solution, NiCl2·6H2O solution, NaBr solution, NaI solution, NaCl solution, Na2SO4 solution, Na2S2O3 solution, Na2S·9H2O solution, NaNO3 solution, NaSCN solution, and NaNO2 solution.

[0022] Subsequently, the initial fluorescence intensity of each film sheet was detected using the aforementioned solid-state fluorescence detection method after immersion in secondary water for 2–5 minutes. Next, the fluorescence intensity of the sensitive film in the presence of different metal ions was tested. Finally, the Hg level was measured. 2+ The fluorescence intensity of the sensitive membrane when coexisting with other metal ions. (This is the result.) Figure 7 The diagrams shown depict the selectivity and anti-interference properties of the sensitive membrane of the present invention for cations. Figure 8 The diagram shows the selectivity and anti-interference performance of the sensitive membrane of this invention for anions. By comparing the changes in fluorescence intensity, it was found that only the mercury ion solution caused a significant change in the fluorescence intensity of the film, indicating that the sensitive membrane of this invention has excellent selectivity and anti-interference performance for mercury ions.

[0023] The preparation method of the present invention has the following advantages:

[0024] 1) CBH / ACG films can exist stably in water, can detect mercury ions in water, and have good selectivity and anti-interference properties. No sample preparation is required during detection, which can improve detection efficiency.

[0025] 2) The synthesis method of CBH / ACG thin films is simple, the materials used in the films are inexpensive, and they can be mass-produced, which holds promise for achieving Hg detection in groundwater. 2+ In-situ detection. Attached Figure Description

[0026] Figure 1 This is a photograph of the CBH / ACG thin film prepared by the method of this invention.

[0027] Figure 2 This is a photograph of the ACG film prepared by the method of this invention.

[0028] Figure 3 This is a scanning electron microscope (SEM) image of the ACG thin film prepared by the method of this invention.

[0029] Figure 4 This is a scanning electron microscope (SEM) image of the CBH / ACG thin film prepared by the method of this invention.

[0030] Figure 5 This is a linear titration diagram of the CBH / ACG thin film prepared by the method of this invention.

[0031] Figure 6 This is a linear fitting curve of the CBH / ACG thin film prepared by the method of this invention.

[0032] Figure 7 This is a graph showing the selectivity and anti-interference properties of the CBH / ACG thin film prepared by the method of this invention for cations.

[0033] Figure 8This is a diagram showing the selectivity and anti-interference properties of the CBH / ACG thin film prepared by the method of this invention for anions. Detailed Implementation

[0034] The preparation of the CBH / ACG sensitive membrane of the present invention will be further explained below with reference to specific embodiments. Example

[0035] Preparation of CBH / ACG sensitive membrane

[0036] 1) 7-(diethylamino)coumarin-3-carboxaldehyde (245 mg, 1 mmol) and 3-methyl-2-benzothiazolidinone hydrazone hydrochloride (233 mg, 1 mmol) were dissolved in hot ethanol (20 mL), and five drops of acetic acid solution were added to the solution. The solution was reacted at 85 °C for 4 h, followed by filtration to obtain a red crude product, which was then washed three times with ethanol to obtain the fluorescent probe CBH. Yield: 211 mg; Yield: 52.2%.

[0037] 2) Chitosan (300 mg), glycerol (900 mg), and 1% acetic acid solution (30 mL) were added to a single-necked flask and stirred until the chitosan was completely dissolved. Then, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (45 mg) was added, and prepolymerization was carried out at room temperature for 6 h to obtain a chitosan-based membrane solution. Finally, the fluorescent probe CBH (10 mg) was added to the chitosan-based membrane solution (30 mL), and stirring was continued for 12 h. The solution was poured into a glass dish and evaporated to obtain a coarse membrane, which was washed three times with water to obtain the desired membrane. Figure 1 The CBH / ACG membrane shown.

[0038] ACG membrane preparation

[0039] 1) Chitosan (300 mg), glycerol (900 mg), and 1% acetic acid solution (30 mL) were added to a single-necked flask and stirred until the chitosan was completely dissolved. Then, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (45 mg) was added, and prepolymerization was carried out at room temperature for 6 h to obtain a chitosan-based film solution. The solution was poured into a glass dish and evaporated to obtain a coarse film, which was washed three times with water to obtain the film shown below. Figure 2 The ACG membrane shown.

Claims

1. A method for preparing a fluorescent sensitive membrane for detecting mercury ions in water, characterized in that, Includes the following steps: 1) 7-(diethylamino)coumarin-3-carboxaldehyde and 3-methyl-2-benzothiazolidinone hydrochloride were co-dissolved in hot ethanol and reacted at 80-90℃ for 4-6 h under the catalysis of acetic acid. The mixture was filtered to obtain a red crude product, which was then washed three times with ethanol to obtain the fluorescent probe CBH. 2) Chitosan and glycerol were co-dissolved in 1% acetic acid solution and stirred until the chitosan was completely dissolved. Then 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride was added and prepolymerized at room temperature for 6-8 h to obtain chitosan-based film solution. 3) Add the fluorescent probe CBH to the chitosan-based membrane solution and continue stirring for 10-12 h. Then pour the solution into a glass dish to evaporate and rinse to obtain the CBH / ACG membrane.

2. The method for preparing a fluorescent sensitive membrane for detecting mercury ions in water as described in claim 1, characterized in that, In step 1), the molar ratio of 7-(diethylamino)coumarin-3-carboxaldehyde and 3-methyl-2-benzothiazolidinone hydrochloride is (1~3):

1.

3. The method for preparing a fluorescent sensitive membrane for detecting mercury ions in water as described in claim 1, characterized in that, In step 1), the temperature of the hot ethanol is 40~50℃.

4. The method for preparing a fluorescent sensitive membrane for detecting mercury ions in water as described in claim 1, characterized in that, In step 2), the mass ratio of chitosan to glycerol is 1:(2~4), and the mass ratio of chitosan to 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride is (6~8):

1.

5. The method for preparing a fluorescent sensitive membrane for detecting mercury ions in water as described in claim 1, characterized in that, In step 3), the concentration of the fluorescent probe CBH in the chitosan-based membrane solution is 0.3~0.9 g / L.

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