A fluorescent chiral Cd-MOF sensor and its application

Abstract

The present invention relates to the field of metal-organic framework materials technology, specifically disclosing a fluorescent chiral Cd-MOF sensor and its applications. The fluorescent chiral Cd-MOF sensor provided by the present invention is prepared using cadmium chloride and 1,4-naphthalenedicarboxylic acid via a solvothermal method. The sensor exhibits excellent fluorescence properties and can detect methyl orange based on its fluorescence intensity.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework (MOF) materials, in particular to a fluorescent chiral Cd-MOF sensor and applications thereof. Background Art

[0002] Organic dyes are used to color a variety of objects and are widely used in industries such as food, pharmaceuticals, polymers, papermaking, textiles, and leather. The discharge of industrial wastewater from printing and dyeing introduces organic dyes into surface and groundwater, causing serious environmental pollution. Most organic dyes are not only toxic and carcinogenic but also resistant to biodegradation, posing a serious threat to human health and aquatic ecosystems even at low concentrations. Consequently, various methods are being developed to remove organic dyes from industrial wastewater.

[0003] Identifying the specific organic dyes present in industrial wastewater and quantifying their concentrations are essential steps before treating it, which requires the use of organic dye detection technologies. Methyl orange is a classic azo dye commonly used as an acid-base indicator in various industrial applications. Several methods for detecting methyl orange have been reported, including liquid chromatography, surface-enhanced Raman spectroscopy, gas chromatography-mass spectrometry, and electrochemical methods. However, these detection methods all have their limitations, such as complex sample preparation, time-consuming and costly operations, and the need for complex and expensive instrumentation. Fluorescence analysis has attracted widespread attention due to its advantages such as low cost, high sensitivity, and fast response time. In addition, studies have found that luminescent metal-organic frameworks (MOFs) are functional crystalline materials with unique structures and excellent luminescence properties, which will be extremely promising in sensing applications.

[0004] Therefore, the present invention aims to provide a fluorescent chiral Cd-MOF sensor and develop a simple, efficient and portable organic dye detection technology based on the sensor. Summary of the Invention

[0005] The main technical problem solved by the present invention is to provide a fluorescent chiral Cd-MOF sensor and also provide its application.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a fluorescent chiral Cd-MOF sensor is prepared by a solvothermal method using cadmium chloride (CdCl2) and 1,4-naphthalene dicarboxylic acid as raw materials.

[0007] The structural formula of 1,4-naphthalene dicarboxylic acid is:

[0008] (denoted as H2NA).

[0009] The molecular formula of the fluorescent chiral Cd-MOF sensor provided by the present invention is: [Cd(NA)DMA] n , where NA represents the group after 1,4-naphthalene dicarboxylic acid loses two protons, and the structure is as follows:

[0010] ;

[0011] n represents a repeating unit.

[0012] As an embodiment of the present invention, the feed mass ratio of the cadmium chloride to the 1,4-naphthalenedicarboxylic acid is (3-4):1.

[0013] As an embodiment of the present invention, the solvothermal method comprises the steps of:

[0014] S1: dissolving cadmium chloride in deionized water to obtain a cadmium chloride aqueous solution;

[0015] dissolving 1,4-naphthalene dicarboxylic acid in dimethylacetamide to obtain a 1,4-naphthalene dicarboxylic acid solution;

[0016] S2: placing the cadmium chloride aqueous solution and the 1,4-naphthalene dicarboxylic acid solution into a polytetrafluoroethylene liner and stirring to mix; placing the polytetrafluoroethylene liner into a high-pressure reactor and heating for reaction; and then cooling to room temperature;

[0017] S3: taking out the reaction solution from the polytetrafluoroethylene liner, centrifuging and separating to obtain a solid, and drying the solid to obtain a fluorescent chiral Cd-MOF sensor.

[0018] As an embodiment of the present invention, the concentration of the cadmium chloride aqueous solution is 20-25 g / L.

[0019] As an embodiment of the present invention, the concentration of the 1,4-naphthalene dicarboxylic acid solution is 25 to 30 g / L.

[0020] As an embodiment of the present invention, in step S2, the cadmium chloride aqueous solution and the 1,4-naphthalene dicarboxylic acid solution are mixed in a volume ratio of (3-6): (1-3).

[0021] As an embodiment of the present invention, in step S2, the heating reaction temperature is 110-130° C., and the reaction time is 60-85 hours.

[0022] As an embodiment of the present invention, in step S3, after taking out the reaction solution, dimethylacetamide is added to the reaction solution, followed by centrifugal separation.

[0023] As an embodiment of the present invention, the number of centrifugal separation treatments is 1 to 5 times.

[0024] As an embodiment of the present invention, when the number of centrifugal separation treatments is 2 or more, the clear liquid needs to be removed after each centrifugal treatment, and then dimethylacetamide is added and centrifugation is continued.

[0025] Preferably, the centrifugal separation is performed under the following conditions: centrifugal treatment at 12000 rpm and 25° C. for 20 min.

[0026] The present invention provides an application of the fluorescent chiral Cd-MOF sensor described in the present invention in the detection of methyl orange.

[0027] The present invention provides a detection platform for detecting methyl orange using the fluorescent chiral Cd-MOF sensor of the present invention. The steps of constructing the detection platform include:

[0028] (1) Adding the fluorescent chiral Cd-MOF sensor into deionized water to prepare suspension A, wherein the concentration of the suspension A is 5 mg / mL;

[0029] The fluorescence intensity of the suspension A is measured at an excitation wavelength of 330 nm. The peak of the fluorescence emission spectrum of the suspension A appears at 400±5 nm, and the peak intensity value of the fluorescence emission spectrum peak of the suspension A is recorded.

[0030] (2) mixing the suspension A with methyl orange solutions of different concentrations to prepare working solutions B of different concentrations;

[0031] The fluorescence intensity of the working solution B was measured at an excitation wavelength of 330 nm. The fluorescence emission peak of each working solution B appeared at 400±5 nm. The peak intensity value of the fluorescence emission spectrum peak of each working solution B was recorded, and a functional relationship between the concentration of the working solution B and the peak-to-peak intensity of the fluorescence emission spectrum was obtained to obtain a detection platform for detecting methyl orange.

[0032] As an embodiment of the present invention, the preparation process of working solution B with different concentrations is as follows:

[0033] Weigh 32.7 mg of methyl orange solid powder and dissolve it in 10 mL of deionized water to obtain a methyl orange solution;

[0034] Prepare 20 2 mL centrifuge tubes and add 190 μL of suspension A to each tube.

[0035] Then, 0.0 μL, 0.5 μL, 1.0 μL, 1.5 μL, 2.0 μL, 2.5 μL, 3.0 μL, 3.5 μL, 4.0 μL, 4.5 μL, 5.0 μL, 5.5 μL, 6.0 μL, 6.5 μL, 7.0 μL, 7.5 μL, 8.0 μL, 8.5 μL, 9.0 μL, and 10.0 μL of the methyl orange solution were added to the 20 2 mL centrifuge tubes, respectively;

[0036] Deionized water was added to the 20 2 mL centrifuge tubes so that the total volume of the liquid in each centrifuge tube was 2 mL, thereby preparing working solutions B with different concentrations.

[0037] The present invention also provides application of the detection platform of the present invention in qualitative and quantitative detection of methyl orange.

[0038] The qualitative test refers to the detection of methyl orange in a sample. The fluorescence intensity of the sample to be tested is measured at an excitation wavelength of 330 nm to obtain the peak intensity value of its fluorescence emission spectrum peak (denoted as A2). This value is then compared with the peak intensity value of the fluorescence emission spectrum peak of suspension A (denoted as A1). If A2 is less than A1, i.e., the peak intensity value of the fluorescence emission spectrum peak of the sample to be tested is lower, then the sample contains methyl orange. Otherwise, the sample does not contain methyl orange.

[0039] Quantitative testing refers to the determination of the methyl orange concentration in a sample. The fluorescence intensity of the sample is measured at an excitation wavelength of 330 nm to obtain the peak intensity of the fluorescence emission spectrum. The methyl orange concentration in the sample is then determined using the functional relationship between the concentration of working solution B and the peak intensity of the fluorescence emission spectrum, as provided in the present invention.

[0040] The fluorescent chiral Cd-MOF sensor provided by the present invention is prepared using a solvothermal method. Cadmium chloride and 1,4-naphthalenedicarboxylic acid are mixed in a high-boiling-point solvent and reacted at high temperature to form Cd-MOF. The sensor exhibits excellent fluorescence properties and can detect methyl orange based on its fluorescence intensity. The detection mechanism is based on fluorescence quenching caused by competitive UV absorption between Cd-MOF and methyl orange. The sensor has a detection limit of as low as 1.10°C. - 10 mol / L, it realizes the accurate detection of methyl orange, and has the characteristics of low cost, high sensitivity and high selectivity, which can meet the detection needs of water environment system safety.

[0041] The present invention also has the following advantages and positive effects:

[0042] 1. The present invention utilizes the fluorescence of 1,4-naphthalenedicarboxylic acid as the fluorescence detection signal of methyl orange. Based on the fluorescence shut-off strategy, it shows a significant change in fluorescence intensity and realizes the rapid detection of methyl orange.

[0043] 2. The sensor can quantitatively detect methyl orange in real time / on-site, making the detection process portable, rapid and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 : is a crystal structure diagram of the Cd-MOF sensor provided in Example 1 of the present invention; wherein (a) is a diagram of the minimum asymmetric unit of Cd-MOF; (b) is a polyhedron diagram of the coordination of Cd atoms; (c) is a three-dimensional structure diagram of Cd-MOF along the c-axis; (d) is a three-dimensional structure diagram of Cd-MOF along the b-axis;

[0045] Figure 2 This is an infrared spectrum of the Cd-MOF sensor provided in Example 1 of the present invention;

[0046] Figure 3 is an X-ray diffraction pattern of the Cd-MOF sensor provided in Example 1 of the present invention;

[0047] Figure 4 is a fluorescence spectrum of the Cd-MOF sensor provided in Example 1 of the present invention;

[0048] Figure 5 is a fluorescence emission spectrum of the working solution B obtained in Example 2 of the present invention;

[0049] Figure 6 is a detection curve diagram obtained in Example 2 of the present invention;

[0050] Figure 7 This is a response time diagram of the fluorescent chiral Cd-MOF sensor obtained in Experimental Example 1 of the present invention detecting methyl orange;

[0051] Figure 8 This is an analysis chart of the selectivity and anti-interference properties of the fluorescent chiral Cd-MOF sensor obtained in Experimental Example 2 of the present invention in detecting methyl orange. DETAILED DESCRIPTION

[0052] The following examples are intended to further illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0053] In the following examples, unless otherwise specified, all the drugs used were commercially available products. Example

[0054] This embodiment provides a fluorescent chiral Cd-MOF sensor, and the preparation steps are as follows:

[0055] S1: Add 91 mg of cadmium chloride to 4 mL of deionized water and sonicate until the cadmium chloride is completely dissolved to obtain a cadmium chloride aqueous solution;

[0056] 27 mg of 1,4-naphthalene dicarboxylic acid was placed in 1 mL of dimethylacetamide (DMA) and sonicated until 1,4-naphthalene dicarboxylic acid was completely dissolved to obtain a 1,4-naphthalene dicarboxylic acid solution;

[0057] S2: The cadmium chloride aqueous solution and 1,4-naphthalene dicarboxylic acid solution obtained in step S1 were placed in a 25 mL polytetrafluoroethylene liner, and stirred at 200 rpm using a magnetic stirrer to mix. The polytetrafluoroethylene liner was placed in a high-pressure reactor, and then placed in an oven at 120°C for heating and reaction for 72 h; and then cooled to room temperature.

[0058] S3: Remove the reaction solution from the polytetrafluoroethylene liner and transfer it to a 50 mL centrifuge tube;

[0059] Add 10 mL of anhydrous DMA and centrifuge at 12,000 rpm and 25°C for 20 min;

[0060] The supernatant was removed, and 10 mL of anhydrous DMA was added, followed by centrifugation at 12,000 rpm and 25°C for 20 min. This step was repeated three times, and the supernatant was removed to obtain a solid precipitate.

[0061] The final precipitate was placed in an oven at 50°C and dried to obtain a fluorescent chiral Cd-MOF sensor.

[0062] The fluorescent chiral Cd-MOF sensor prepared in this example was characterized, and the crystal structure of the obtained Cd-MOF sensor is shown in FIG. Figure 1 As shown, the infrared spectrum is shown in Figure 2 The X-ray diffraction pattern is shown in Figure 3 The fluorescence spectrum is shown in Figure 4 shown.

[0063] Figure 1 (a) is the minimum asymmetric unit diagram of Cd-MOF; (b) is the polyhedron diagram of Cd atomic coordination; (c) is the three-dimensional structure diagram of Cd-MOF along the c-axis; (d) is the three-dimensional structure diagram of Cd-MOF along the b-axis. Example

[0064] This embodiment provides a detection platform for detecting methyl orange based on the fluorescent chiral Cd-MOF sensor provided in Example 1, and the construction steps include:

[0065] (1) The fluorescent chiral Cd-MOF sensor prepared in Example 1 was added to deionized water to prepare suspension A. The concentration of suspension A was 5 mg / mL.

[0066] (2) Suspension A is mixed with methyl orange solutions of different concentrations to prepare working solutions B of different concentrations. The specific preparation process is as follows:

[0067] Weigh 32.7 mg of methyl orange solid powder and dissolve it in 10 mL of deionized water to obtain a methyl orange solution;

[0068] Prepare 20 2 mL centrifuge tubes and add 190 μL of suspension A to each tube.

[0069] Then, 0.0 μL, 0.5 μL, 1.0 μL, 1.5 μL, 2.0 μL, 2.5 μL, 3.0 μL, 3.5 μL, 4.0 μL, 4.5 μL, 5.0 μL, 5.5 μL, 6.0 μL, 6.5 μL, 7.0 μL, 7.5 μL, 8.0 μL, 8.5 μL, 9.0 μL, and 10.0 μL of methyl orange solution were added to 20 2 mL centrifuge tubes, respectively;

[0070] Add deionized water to 20 2 mL centrifuge tubes so that the total volume of liquid in each centrifuge tube is 2 mL to prepare working solutions B with different concentrations.

[0071] (3) Under an excitation wavelength of 330 nm, measure the fluorescence intensity of suspension A. The peak of the fluorescence emission spectrum of suspension A appears at 400 ± 5 nm. Record the peak intensity value of the fluorescence emission spectrum of suspension A.

[0072] The fluorescence intensity of each working solution B was measured at an excitation wavelength of 330 nm. The fluorescence emission peak of each working solution B appeared at 400 ± 5 nm. The peak intensity value of the fluorescence emission spectrum peak of each working solution B was recorded. The functional relationship between the concentration of working solution B and the peak intensity of the fluorescence emission spectrum was obtained.

[0073] The functional relationship between the peak-to-peak intensity of the fluorescence emission spectrum and the concentration of methyl orange is:

[0074] Y=0.01957X-0.11467(R 2 =0.99), the detection limit was 0.101 nM;

[0075] The obtained detection curve is shown in Figure 6 As shown;

[0076] Obtain a detection platform for detecting methyl orange.

[0077] The fluorescence emission spectrum of working solution B in this example is shown in Figure 5 The peak intensity value of the fluorescence emission spectrum peak of working solution B containing different concentrations of methyl orange will decrease with the increase of methyl orange concentration, and show a continuous downward trend.

[0078] This experimental example investigates the time response of the fluorescent chiral Cd-MOF sensor for detecting methyl orange provided in Example 1, and specifically includes the following steps:

[0079] (1) The fluorescent chiral Cd-MOF sensor prepared in Example 1 was added to deionized water to prepare suspension A. The concentration of suspension A was 5 mg / mL.

[0080] Weigh 32.7 mg of methyl orange solid powder and dissolve it in 10 mL of deionized water to obtain a methyl orange solution;

[0081] (2) Take 270 μL of suspension A and place it in a cuvette. Add 30 μL of methyl orange solution to form mixed solution C (the concentration of methyl orange in mixed solution C is 0.327 mg / mL):

[0082] At an excitation wavelength of 330 nm, the fluorescence intensity of mixed solution C was measured every 5 seconds until the fluorescence intensity no longer changed; a series of peak intensity values ​​of the fluorescence intensity of mixed solution C at different times were obtained, and it was found that it decreased with time, showing a continuous downward trend, and eventually stopped changing.

[0083] Figure 7 This is the response time diagram of the fluorescent chiral Cd-MOF sensor obtained in this experimental example to detect methyl orange. The experiment shows that the response time of the fluorescent chiral Cd-MOF sensor to methyl orange is 20S.

[0084] This experimental example investigates the selectivity and anti-interference performance of the fluorescent chiral Cd-MOF sensor for detecting methyl orange based on Example 1, and specifically includes the following steps:

[0085] (1) Prepare several 2 mL centrifuge tubes and add 250 μL of suspension A (suspension A is the same as in Experiment 1, with a concentration of 5 mg / mL) to each tube.

[0086] (2) Add interfering substances to the centrifuge tubes at a concentration of 320 μM. After 2 min of reaction, measure the fluorescence spectra of the reaction systems. The interfering substances are NaCl, KCl, NH4Cl, Na2SO4, glucose, creatine, glutamic acid (Glu), urea, and creatinine.

[0087] (3) Methyl orange solution was added to each reaction system. The methyl orange solution was the same as that in Experimental Example 1, so that the concentration of methyl orange in each reaction system was 0.327 mg / mL. The reaction was carried out for 2 min, and the fluorescence spectrum of each reaction system was measured.

[0088] Figure 8 This is an analysis diagram of the selectivity and anti-interference of the fluorescent chiral Cd-MOF sensor obtained in this experimental example for detecting methyl orange.

[0089] Figure 8 Middle: The initial blue color represents the fluorescence intensity of suspension A, and the orange color represents the fluorescence intensity after methyl orange was added to suspension A (the concentration of methyl orange was 0.327 mg / mL).

[0090] Figure 8 Except for the initial color, blue represents the fluorescence intensity of each reaction system after the interfering substance is added in step (2), and orange represents the fluorescence intensity of each reaction system after the methyl orange is added in step (3).

[0091] Experiments have shown that the presence of the above interfering substances did not cause a significant change in the color of the reaction solution. In contrast, the fluorescence intensity decreased significantly after the introduction of methyl orange. In the selectivity test, it is worth noting that interfering substances such as common compounds in wastewater have little effect on Cd-MOF, and their fluorescence intensity ratio is extremely insignificant compared to methyl orange. These results show that the Cd-MOF-based methyl orange detection method has excellent selectivity and anti-interference ability, that is, the established detection platform has significant selectivity and can specifically distinguish and detect methyl orange despite the presence of potential interfering compounds.

[0092] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or any direct or indirect application in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. Application of a fluorescent chiral Cd-MOF sensor in the detection of methyl orange, wherein the fluorescent chiral Cd-MOF sensor is prepared using cadmium chloride and 1,4-naphthalenedicarboxylic acid as raw materials via a solvothermal method; the solvothermal method comprises the following steps: S1: dissolving cadmium chloride in deionized water to obtain a cadmium chloride aqueous solution; dissolving 1,4-naphthalene dicarboxylic acid in dimethylacetamide to obtain a 1,4-naphthalene dicarboxylic acid solution; S2: placing the cadmium chloride aqueous solution and the 1,4-naphthalene dicarboxylic acid solution into a polytetrafluoroethylene liner and stirring to mix; placing the polytetrafluoroethylene liner into a high-pressure reactor and heating for reaction; and then cooling to room temperature; S3: removing the reaction solution from the polytetrafluoroethylene liner, centrifuging to obtain a solid, and drying the solid to obtain a fluorescent chiral Cd-MOF sensor; in, The concentration of the cadmium chloride aqueous solution is 20-25 g / L; the concentration of the 1,4-naphthalene dicarboxylic acid solution is 25-30 g / L; In step S2, the cadmium chloride aqueous solution and the 1,4-naphthalene dicarboxylic acid solution are mixed in a volume ratio of (3-6): (1-3); In step S2, the heating reaction temperature is 110-130° C., and the reaction time is 60-85 hours.

2. The use according to claim 1, characterized in that In step S3, after taking out the reaction solution, dimethylacetamide is added to the reaction solution, followed by centrifugation.

3. A detection platform for detecting methyl orange using a fluorescent chiral Cd-MOF sensor, characterized in that: The build steps include: (1) Adding the fluorescent chiral Cd-MOF sensor into deionized water to prepare suspension A, wherein the concentration of the suspension A is 5 mg / mL; The fluorescence intensity of the suspension A is measured at an excitation wavelength of 330 nm. The peak of the fluorescence emission spectrum of the suspension A appears at 400±5 nm, and the peak intensity value of the fluorescence emission spectrum peak of the suspension A is recorded. (2) mixing the suspension A with methyl orange solutions of different concentrations to prepare working solutions B of different concentrations; The fluorescence intensity of the working solution B was measured at an excitation wavelength of 330 nm. The fluorescence emission peak of each working solution B appeared at 400±5 nm. The peak intensity value of the fluorescence emission spectrum peak of each working solution B was recorded to obtain a functional relationship between the concentration of the working solution B and the peak-to-peak intensity of the fluorescence emission spectrum, thereby obtaining a detection platform for detecting methyl orange. The preparation process of working solution B with different concentrations is as follows: Weigh 32.7 mg of methyl orange solid powder and dissolve it in 10 mL of deionized water to obtain a methyl orange solution; Prepare 20 2 mL centrifuge tubes and add 190 μL of suspension A to each tube. Then, 0.0 μL, 0.5 μL, 1.0 μL, 1.5 μL, 2.0 μL, 2.5 μL, 3.0 μL, 3.5 μL, 4.0 μL, 4.5 μL, 5.0 μL, 5.5 μL, 6.0 μL, 6.5 μL, 7.0 μL, 7.5 μL, 8.0 μL, 8.5 μL, 9.0 μL, and 10.0 μL of the methyl orange solution were added to the 20 2 mL centrifuge tubes, respectively; Deionized water was added to the 20 2 mL centrifuge tubes so that the total volume of the liquid in each centrifuge tube was 2 mL, to prepare working solutions B with different concentrations; The fluorescent chiral Cd-MOF sensor is prepared using cadmium chloride and 1,4-naphthalene dicarboxylic acid as raw materials through a solvothermal method; the solvothermal method comprises the following steps: S1: dissolving cadmium chloride in deionized water to obtain a cadmium chloride aqueous solution; dissolving 1,4-naphthalene dicarboxylic acid in dimethylacetamide to obtain a 1,4-naphthalene dicarboxylic acid solution; S2: placing the cadmium chloride aqueous solution and the 1,4-naphthalene dicarboxylic acid solution into a polytetrafluoroethylene liner and stirring to mix; placing the polytetrafluoroethylene liner into a high-pressure reactor and heating for reaction; and then cooling to room temperature; S3: removing the reaction solution from the polytetrafluoroethylene liner, centrifuging to obtain a solid, and drying the solid to obtain a fluorescent chiral Cd-MOF sensor; Wherein, the concentration of the cadmium chloride aqueous solution is 20-25 g / L; the concentration of the 1,4-naphthalene dicarboxylic acid solution is 25-30 g / L; In step S2, the cadmium chloride aqueous solution and the 1,4-naphthalene dicarboxylic acid solution are mixed in a volume ratio of (3-6): (1-3); In step S2, the heating reaction temperature is 110-130° C., and the reaction time is 60-85 hours.

4. The detection platform according to claim 3, characterized in that: In step S3, after taking out the reaction solution, dimethylacetamide is added to the reaction solution, followed by centrifugation.

5. Use of the detection platform according to claim 3 or 4 in the qualitative and quantitative detection of methyl orange.

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