Fluorescent chiral Cd-MOF sensor and application

Abstract

The invention relates to the technical field of metal organic framework materials, particularly discloses a fluorescent chiral Cd-MOF sensor and also discloses application of the fluorescent chiral Cd-MOF sensor. The fluorescent chiral Cd-MOF sensor provided by the invention is prepared by taking cadmium chloride and 1, 4-naphthalic acid as raw materials through a solvothermal method. The sensor has an excellent fluorescence luminescence property, and can detect methyl orange based on the fluorescence intensity of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of metal-organic framework (MOF) materials, and particularly to a fluorescent chiral Cd-MOF sensor, and also relates to its application. Background Art

[0002] Organic dyes are used to color various objects and are widely used in industries such as food, pharmaceuticals, polymers, paper, textiles, and leather. The discharge of industrial wastewater generated by printing and dyeing introduces organic dyes into surface water and groundwater, causing serious environmental pollution. Most organic dyes are not only toxic and carcinogenic but also have anti-biodegradability, posing a serious threat to human health and the water ecosystem even at low concentrations. Therefore, various methods have been developed to remove organic dyes from industrial wastewater.

[0003] Identifying the specific organic dyes contained in industrial wastewater and quantifying their concentrations before treating the wastewater is an essential step, which relies on organic dye detection techniques. Methyl orange is a classic azo dye and is commonly used as an acid-base indicator in various industrial applications. Several detection methods for methyl orange have been reported, including liquid chromatography, surface-enhanced Raman spectroscopy, gas chromatography-mass spectrometry, electrochemistry, etc. However, these detection methods all have their respective limitations, such as complex sample processing, long operation time and high cost, and the need for complex and expensive instrumentation. Fluorescence analysis has attracted wide attention due to its advantages such as low cost, high sensitivity, and fast response time. Moreover, it has been found that luminescent metal-organic frameworks (MOFs) are functional crystalline materials with unique structures and excellent luminescent properties and are very 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 technique based on this sensor. Summary of the Invention

[0005] The main technical problem to be 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 problem, the technical solution adopted by the present invention is: a fluorescent chiral Cd-MOF sensor, using cadmium chloride (CdCl 2 ) and 1,4-naphthalenedicarboxylic acid as raw materials, and preparing the fluorescent chiral Cd-MOF sensor by a solvothermal method.

[0007] The structural formula of 1,4-naphthalenedicarboxylic acid is: (denoted as H 2 NA).

[0008] 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 removing two protons from 1,4-naphthalenedicarboxylic acid, and the structure is as follows: ; n represents the repeating unit.

[0009] As an embodiment of the present invention, the mass ratio of the cadmium chloride to the 1,4-naphthalenedicarboxylic acid is (3-4):1.

[0010] As an embodiment of the present invention, the solvothermal method includes the steps of: S1: Dissolve cadmium chloride in deionized water to obtain an aqueous cadmium chloride solution; Dissolve 1,4-naphthalenedicarboxylic acid in dimethylacetamide to obtain a 1,4-naphthalenedicarboxylic acid solution; S2: Put the aqueous cadmium chloride solution and the 1,4-naphthalenedicarboxylic acid solution into a polytetrafluoroethylene inner liner, stir and mix; put the polytetrafluoroethylene inner liner into a high-pressure reactor for heating reaction; then cool to room temperature; S3: Take out the reaction solution from the polytetrafluoroethylene inner liner, centrifuge to separate the solid, and obtain the fluorescent chiral Cd-MOF sensor after drying.

[0011] As an embodiment of the present invention, the concentration of the aqueous cadmium chloride solution is 20-25 g / L.

[0012] As an embodiment of the present invention, the concentration of the 1,4-naphthalenedicarboxylic acid solution is 25-30 g / L.

[0013] As an embodiment of the present invention, in step S2, the aqueous cadmium chloride solution and the 1,4-naphthalenedicarboxylic acid solution are mixed in a volume ratio of (3-6):(1-3).

[0014] 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.

[0015] As an embodiment of the present invention, in step S3, after taking out the reaction solution, add dimethylacetamide to the reaction solution, and then centrifuge.

[0016] As an embodiment of the present invention, the number of centrifugation treatments is 1-5 times.

[0017] As an embodiment of the present invention, when the number of centrifugation treatments is 2 or more times, the supernatant needs to be removed after each centrifugation treatment, and then dimethylacetamide is added for further centrifugation treatment.

[0018] Preferably, the processing conditions for centrifugal separation are: centrifugal treatment for 20 min at 12,000 rpm and 25 °C.

[0019] The present invention provides an application of the fluorescent chiral Cd-MOF sensor described in the present invention in the detection of methyl orange.

[0020] The present invention provides a detection platform for detecting methyl orange using the fluorescent chiral Cd-MOF sensor described in the present invention. The construction steps of the detection platform include: (1) Add the fluorescent chiral Cd-MOF sensor to deionized water to prepare a suspension A with a concentration of 5 mg / mL. Under an excitation wavelength of 330 nm, measure the fluorescence intensity of the suspension A. The peak of the fluorescence emission spectrum of the suspension A appears at 400 ± 5 nm. Record the peak intensity value of the fluorescence emission spectrum peak of the suspension A. (2) Mix the suspension A with methyl orange solutions of different concentrations to prepare working solutions B with different concentrations. Under an excitation wavelength of 330 nm, measure the fluorescence intensity of the working solutions B. The fluorescence emission peaks of each working solution B all appear at 400 ± 5 nm. Record the peak intensity values of the fluorescence emission spectrum peaks of each working solution B to obtain the functional relationship between the concentration of the working solution B and the peak intensity of the fluorescence emission spectrum, and obtain a detection platform for detecting methyl orange.

[0021] As an embodiment of the present invention, the preparation process of the working solutions 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 the suspension A to each of them. Then, add 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, 10.0 μL of the methyl orange solution to the 20 2-mL centrifuge tubes respectively. Add deionized water to the 20 2-mL centrifuge tubes so that the total volume of the liquid in each centrifuge tube is 2 mL, and prepare working solutions B with different concentrations.

[0022] The present invention also provides an application of the detection platform described in the present invention in the qualitative and quantitative detection of methyl orange.

[0023] Among them, the qualitative detection refers to the detection of whether methyl orange is contained in the sample. By measuring the fluorescence intensity of the sample to be tested at an excitation wavelength of 330 nm, the peak intensity value of its fluorescence emission spectrum peak (denoted as A 2 ), and then comparing it with the peak intensity value of the fluorescence emission spectrum peak of suspension A (denoted as A 1 ), if A 2 < A 1 , that is, the peak intensity value of the fluorescence emission spectrum peak of the sample to be tested decreases, it indicates that methyl orange is contained in the sample, otherwise it does not contain methyl orange.

[0024] The quantitative detection refers to the detection of the concentration of methyl orange contained in the sample. By measuring the fluorescence intensity of the sample to be tested at an excitation wavelength of 330 nm, the peak intensity value of its fluorescence emission spectrum peak is obtained, and then through the functional relationship between the concentration of working solution B provided by the present invention and the peak intensity of the fluorescence emission spectrum peak, the concentration of methyl orange contained in the sample to be tested is obtained.

[0025] The fluorescent chiral Cd-MOF sensor provided by the present invention is prepared by a solvothermal method. By mixing cadmium chloride and 1,4-naphthalenedicarboxylic acid in a high-boiling solvent and reacting at high temperature to generate Cd-MOF. This sensor has excellent fluorescence emission properties and can detect methyl orange based on its fluorescence intensity. The mechanism of the detection method is based on the ultraviolet competitive absorption between Cd-MOF and methyl orange, resulting in fluorescence quenching. The detection limit of the fluorescence response of this sensor is as low as 1.10´10 - 10 mol / L, realizing the precise detection of methyl orange, and having the characteristics of low cost, high sensitivity, and high selectivity, which can meet the detection requirements for the safety of the water environment system.

[0026] The present invention also has the following advantages and positive effects: 1. The present invention uses the fluorescence of 1,4-naphthalenedicarboxylic acid as the fluorescence detection signal for methyl orange. Based on the fluorescence turn-off strategy, it shows obvious fluorescence intensity changes and realizes the rapid detection of methyl orange; 2. This sensor can quantitatively detect methyl orange in real time / on-site, making the detection process portable, fast and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the crystal structure diagram of the Cd-MOF sensor provided in Embodiment 1 of the present invention; among them, (a) is the diagram of the smallest asymmetric unit of Cd-MOF; (b) is the polyhedron diagram of Cd atom 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; Figure 2It is the infrared spectrum of the Cd-MOF sensor provided in Embodiment 1 of the present invention; Figure 3 It is the X-ray diffraction pattern of the Cd-MOF sensor provided in Embodiment 1 of the present invention; Figure 4 It is the fluorescence spectrum of the Cd-MOF sensor provided in Embodiment 1 of the present invention; Figure 5 It is the fluorescence emission spectrum of the working solution B obtained in Embodiment 2 of the present invention; Figure 6 It is the detection curve obtained in Embodiment 2 of the present invention; Figure 7 It is the response time graph of the fluorescence chiral Cd-MOF sensor for detecting methyl orange obtained in Experimental Example 1 of the present invention; Figure 8 It is the selectivity and anti-interference analysis graph of the fluorescence chiral Cd-MOF sensor for detecting methyl orange obtained in Experimental Example 2 of the present invention. Detailed implementation manners

[0028] The technical solutions of the present invention will be described in detail below through specific embodiments. The following embodiments are intended to further illustrate the content of the present invention in detail, rather than limiting the scope of protection of the claims of the present invention.

[0029] In the following examples, unless otherwise specified, the reagents used are all commercially available products. Embodiment

[0030] This embodiment provides a fluorescence chiral Cd-MOF sensor, and the preparation steps are as follows: S1: Put 91 mg of cadmium chloride into 4 mL of deionized water, and ultrasonically treat until the cadmium chloride is completely dissolved to obtain an aqueous cadmium chloride solution; Put 27 mg of 1,4-naphthalenedicarboxylic acid into 1 mL of dimethylacetamide (DMA), and ultrasonically treat until the 1,4-naphthalenedicarboxylic acid is completely dissolved to obtain a 1,4-naphthalenedicarboxylic acid solution; S2: Put the aqueous cadmium chloride solution and 1,4-naphthalenedicarboxylic acid solution obtained in step S1 into a 25 mL polytetrafluoroethylene inner liner, turn on the magnetic stirrer and stir at a speed of 200 rpm for mixing; put the polytetrafluoroethylene inner liner into a high-pressure reaction kettle, and then place it in an oven at 120 °C for heating reaction for 72 h; then cool to room temperature; S3: Take out the reaction solution from the polytetrafluoroethylene inner liner, and transfer the reaction solution to a 50 mL centrifuge tube; Add 10 mL of anhydrous DMA, and centrifuge at 12000 rpm and 25 °C for 20 min; The supernatant was removed, and then 10 mL of anhydrous DMA was added. The mixture was centrifuged at 12,000 rpm and 25 °C for 20 min; this step was repeated three times. After removing the supernatant, a solid precipitate was obtained. The finally obtained precipitate was placed in an oven at 50 °C for drying to obtain a fluorescent chiral Cd-MOF sensor.

[0031] The fluorescent chiral Cd-MOF sensor prepared in this example was characterized. The crystal structure diagram of the obtained Cd-MOF sensor is shown in Figure 1 as follows, the infrared spectrum is shown in Figure 2 as follows, the X-ray diffraction pattern is shown in Figure 3 as follows, and the fluorescence spectrum is shown in Figure 4 as follows.

[0032] Figure 1 In (a) is the diagram of the smallest asymmetric unit of Cd-MOF; (b) is the polyhedron diagram of Cd atom 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

[0033] This example provides a detection platform for detecting methyl orange based on the fluorescent chiral Cd-MOF sensor provided in Example 1. The construction steps include: (1) The fluorescent chiral Cd-MOF sensor prepared in Example 1 was added to deionized water to make a suspension A, and the concentration of the suspension A was 5 mg / mL. (2) The suspension A was mixed with methyl orange solutions of different concentrations to make working solutions B with different concentrations. The specific preparation process was as follows: 32.7 mg of methyl orange solid powder was weighed and dissolved in 10 mL of deionized water to obtain a methyl orange solution. Twenty 2-mL centrifuge tubes were prepared, and 190 μL of the suspension A was added to each of them. 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, 10.0 μL of the methyl orange solution were respectively added to the twenty 2-mL centrifuge tubes. Deionized water was added to the twenty 2-mL centrifuge tubes to make the total volume of the liquid in each centrifuge tube 2 mL, and working solutions B with different concentrations were prepared. (3)At an excitation wavelength of 330 nm, the fluorescence intensity of suspension A was measured. The peak of the fluorescence emission spectrum of suspension A appeared at 400 ± 5 nm, and the peak intensity value of the fluorescence emission spectrum peak of suspension A was recorded. At an excitation wavelength of 330 nm, the fluorescence intensity of each working solution B was measured. The fluorescence emission peaks of each working solution B all appeared at 400 ± 5 nm, and the peak intensity values of the fluorescence emission spectrum peaks of each working solution B were recorded; the functional relationship between the concentration of working solution B and the peak intensity of the fluorescence emission spectrum peak was obtained. The functional relationship between the peak intensity of the obtained fluorescence emission spectrum peak and the methyl orange concentration was: Y = 0.01957X - 0.11467 (R 2 = 0.99), and the detection limit was 0.101 nM; The obtained detection curve graph is shown in Figure 6 as follows; A detection platform for detecting methyl orange was obtained.

[0034] The fluorescence emission spectrum graph of working solution B in this example is shown in Figure 5 , and the peak intensity values of the fluorescence emission spectrum peaks of working solution B containing different concentrations of methyl orange will decrease with the increase of the methyl orange concentration, and show a continuous downward trend.

[0035] This experimental example investigated the time responsiveness of the fluorescence chiral Cd-MOF sensor for detecting methyl orange provided in Example 1, and specifically included the following steps: (1)The fluorescence chiral Cd-MOF sensor prepared in Example 1 was added to deionized water to form suspension A, and the concentration of suspension A was 5 mg / mL; 32.7 mg of methyl orange solid powder was weighed and dissolved in 10 mL of deionized water to obtain a methyl orange solution; (2)270 μL of suspension A was taken and placed in a cuvette, and 30 μL of the methyl orange solution was added to form a mixed solution C (the concentration of methyl orange in the mixed solution C was 0.327 mg / mL): At an excitation wavelength of 330 nm, the fluorescence intensity of the 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 the mixed solution C at different times were obtained, and it was found that they would decrease with the increase of time, showing a continuous downward trend, and finally no longer changed.

[0036] Figure 7 is the response time graph of the fluorescence chiral Cd-MOF sensor for detecting methyl orange obtained in this experimental example. Experiments have proved that the response time of the fluorescence chiral Cd-MOF sensor to methyl orange is 20S.

[0037] This experimental example investigated the selectivity and anti-interference ability of the fluorescent chiral Cd-MOF sensor provided in Example 1 for detecting methyl orange, and specifically included the following steps: (1) Prepare several 2 mL centrifuge tubes, and add 250 μL of suspension A (suspension A is the same as in Experimental Example 1, with a concentration of 5 mg / mL) to each of them; (2) Add interfering substances to the centrifuge tubes. The concentration of each interfering substance is 320 μM. After reacting for 2 min, measure the fluorescence spectra of the resulting reaction systems; the interfering substances are NaCl, KCl, NH 4 Cl, Na 2 SO 4 , glucose, creatine, glutamic acid (Glu), urea, and creatinine; (3) Add methyl orange solution to each reaction system. The methyl orange solution is the same as in Experimental Example 1, so that the concentration of methyl orange in each reaction system is 0.327 mg / mL. React for 2 min, and then measure the fluorescence spectra of the resulting reaction systems.

[0038] Figure 8 is the analysis diagram of the selectivity and anti-interference ability of the fluorescent chiral Cd-MOF sensor for detecting methyl orange obtained in this experimental example.

[0039] Figure 8 In : Initially, the blue color represents the fluorescence intensity of suspension A, and the orange color represents the fluorescence intensity after adding methyl orange to suspension A (where the concentration of methyl orange is 0.327 mg / mL).

[0040] Figure 8 Except for the initial state, in, the blue color represents the fluorescence intensity of each reaction system after adding the interfering substance in step (2), and the orange color represents the fluorescence intensity of each reaction system after adding methyl orange in step (3).

[0041] 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, after introducing methyl orange, the fluorescence intensity decreased significantly. 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 ratios are extremely insignificant compared to methyl orange. These results indicate 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.

[0042] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent transformation made using the content of the specification of the present invention, directly or indirectly applied in other related technical fields, shall be included within the patent protection scope of the present invention.

Claims

1. A fluorescent chiral Cd-MOF sensor, characterized in that: The fluorescent chiral Cd-MOF sensor is prepared by a solvothermal method using cadmium chloride and 1,4-naphthalene dicarboxylic acid as raw materials.

2. The fluorescent chiral Cd-MOF sensor according to claim 1, characterized in that: The feed mass ratio of the cadmium chloride to the 1,4-naphthalene dicarboxylic acid is (3-4):

1.

3. The fluorescent chiral Cd-MOF sensor according to claim 1, characterized in that: The solvothermal method comprises the steps of: 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 to react; and then cooling to room temperature; 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.

4. The fluorescent chiral Cd-MOF sensor according to claim 3, characterized in that: 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.

5. The fluorescent chiral Cd-MOF sensor according to claim 3, characterized in that: 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).

6. The fluorescent chiral Cd-MOF sensor according to claim 3, characterized in that: In step S2, the heating reaction temperature is 110-130°C, and the reaction time is 60-85 hours.

7. The fluorescent chiral Cd-MOF sensor 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 centrifugal separation.

8. Use of the fluorescent chiral Cd-MOF sensor according to any one of claims 1 to 7 in the detection of methyl orange.

9. A detection platform for detecting methyl orange using the fluorescent chiral Cd-MOF sensor according to any one of claims 1 to 7, characterized in that: The build steps include: (1) adding the fluorescent chiral Cd-MOF sensor into deionized water to prepare a suspension A, wherein the concentration of the suspension A is 5 mg / mL; Under an excitation wavelength of 330 nm, the fluorescence intensity of the suspension A is measured, the peak of the fluorescence emission spectrum of the suspension A appears at 400±5 nm, and the peak intensity value of the peak of the fluorescence emission spectrum 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; Under an excitation wavelength of 330 nm, the fluorescence intensity of the working solution B is measured, and the fluorescence emission peak of each working solution B appears at 400±5 nm. The peak intensity value of the fluorescence emission spectrum peak of each working solution B is recorded, and the functional relationship between the concentration of the working solution B and the peak-to-peak intensity of the fluorescence emission spectrum is obtained to obtain a detection platform for detecting methyl orange; Among them, the preparation process of working solution B with different concentrations is: 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 into 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, thereby preparing working solutions B with different concentrations.

10. Use of the detection platform according to claim 9 in qualitative and quantitative detection of methyl orange.

Images