Preparation method and application of RE-MOF-coated C60 / beta-CD / GCE electrode for detecting dichlorophenol in water body

Abstract

The invention belongs to the technical field of electrochemical analysis, discloses a preparation method and application of an RE-MOF-coated C60 / beta-CD / GCE electrode for detecting dichlorophenol in a water body, and particularly relates to an electrochemical sensor based on a rare earth metal organic framework, fullerene and water-soluble beta-cyclodextrin ternary nano composite material, which is used for detecting 2, 4-dichlorophenol in the water body. And 2, 2-methylenebis (4-chlorophenol) is obtained. The electrical conductivity of the composite material is remarkably improved by embedding RE-MOF into C60, then RE-MOF is compounded with beta-CD, and the electro-catalytic oxidation activity of Dcp is remarkably enhanced by utilizing the subject-object recognition effect of RE-MOF and beta-CD. The prepared electrode has low detection limit and good reproducibility, stability and selectivity, is successfully applied to detection of Dcp in an actual water sample, and shows good recovery rate. The electrode has the advantages of simplicity, convenience, low cost, high efficiency and high sensitivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical analysis, and relates to a preparation method and application of a RE-MOF@C 60 / β-CD / GCE electrode for detecting dichlorophenol in water Background Art

[0002] 2,2-Methylenebis(4-chlorophenol) (dichlorophenol, Dcp), as a highly toxic environmental pollutant, has a low concentration and is stable and not easily degraded in the environment. High-efficiency detection of it has become a current research hotspot. Traditional methods such as high-performance liquid chromatography, gas chromatography, capillary electrophoresis, solid-phase microextraction, and flow injection analysis have defects such as high detection costs, time-consuming, and complicated sample processing procedures. Based on this, the present invention has developed an electrochemical sensor based on a ternary nanocomposite of rare earth metal-organic framework (RE-MOF), fullerene (C 60 ) and water-soluble β-cyclodextrin (β-CD), and used it to detect dichlorophenol in water. Embedding RE-MOF into C 60 can significantly improve the conductivity of the composite material and thus enhance the electrocatalytic performance of the material. Further compounding with β-CD, due to the host-guest recognition of β-CD, the RE-MOF@C 60 / β-CD modified electrode shows excellent electrocatalytic activity for the oxidation of Dcp. The developed sensor realizes the sensitive detection of Dcp with a low detection limit. In addition, the sensor also has good reproducibility, stability, and selectivity. The sensor has been successfully applied to the detection of Dcp in actual water samples and has a good recovery rate. The sensor proposed by the present invention has the advantages of simplicity, low cost, high efficiency, high sensitivity, and high specificity, providing an important basis for the specific recognition and highly selective detection of dichlorophenol in actual water samples. Summary of the Invention

[0003] Aiming at the technical problems of low sensitivity and poor detection limit in the prior art, the present invention provides an electrochemical sensor based on a composite material of rare earth metal-organic framework (RE-MOF), fullerene (C 60 ), and β-cyclodextrin (β-CD), which has the advantages of low cost, simple preparation, sensitivity, rapidity, and good selectivity, and can realize the rapid and sensitive detection of dichlorophenol in water.

[0004] The technical solution of the present invention is as follows:

[0005] An electrochemical sensor for detecting dichlorophenol in water is composed of a RE-MOF@C 60 / β-CD composite material modified glassy carbon electrode as the working electrode and a three-electrode system including a counter electrode and a reference electrode, and constitutes an electrochemical sensor for detecting dichlorophenol with an electrochemical workstation.Figure 1 Schematic diagram of the sensor device of the present invention. The preparation of the sensor and its application to dichlorophenol in water body include the following steps:

[0006] (1) Preparation of RE-MOF@C 60 / β-CD composite material: Ultrasonically dissolve rare earth metal salts and organic ligands in organic solvents respectively to obtain two solutions; Mix C 60 , β-CD with the two solutions, and perform magnetic stirring; After reacting for a certain time under certain temperature conditions, cool, centrifuge and wash the product to obtain a precipitate, and then dry to obtain RE-MOF@C 60 / β-CD composite material;

[0007] (2) Preparation of electrochemical sensor: Ultrasonically disperse the RE-MOF@C 60 / β-CD composite material with an organic solvent to obtain a dispersion; Before modifying the glassy carbon electrode, polish the glassy carbon electrode with alumina powders with particle sizes of 1.0 μm and 0.05 μm respectively, and then ultrasonically clean it in water, ethanol and water in sequence; Drop the dispersion onto the surface of the polished glassy carbon electrode and dry it to obtain RE-MOF@C 60 / β-CD / GCE electrode. Prepare RE-MOF / GCE, β-CD / GCE, C 60 / GCE and RE-MOF@C 60 / GCE under the same conditions.

[0008] Electrochemical detection of dichlorophenol: Connect the working electrode RE-MOF@C 60 / β-CD / GCE, the counter electrode and the reference electrode to an electrochemical workstation, assemble them into an electrochemical sensor, and use electrochemical technology to electrochemically detect dichlorophenol in the water body. The electrochemical workstation records the current-voltage change situation, obtains the current-voltage curve, reads the current values corresponding to different dichlorophenol concentrations, and plots the current-concentration linear working curve.

[0009] Preferably, the rare earth metal salts described in step (1) include but are not limited to one or more mixtures of nitrates of rare earth metals or chlorides of rare earth metals.

[0010] Preferably, the organic ligands described in step (1) include but are not limited to one or more mixtures of dimethylimidazole, terephthalic acid, aminoterephthalic acid, dihydroxyterephthalic acid.

[0011] Preferably, the organic solvents described in steps (1) and (2) include but are not limited to one or more mixtures of methanol, ethanol, acetonitrile, dichloromethane, dimethyl sulfoxide, toluene, acetone, tetrahydrofuran, isopropanol, n-butanol, N, N-dimethylformamide (DMF).

[0012] Preferably, the time for magnetic stirring in step (1) is 0.1 to 96 hours.

[0013] Preferably, in step (1), the certain temperature is 60 to 250 °C and the certain time is 0.5 to 96 hours.

[0014] The reference electrode includes, but is not limited to, Ag / AgCl electrode, saturated calomel electrode, and mercury-mercurous sulfate electrode.

[0015] Preferably, the counter electrode includes, but is not limited to, a platinum wire or platinum sheet electrode.

[0016] Preferably, the electrochemical technique includes, but is not limited to, cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, and linear sweep voltammetry.

[0017] Preferably, the water body includes, but is not limited to, river water, lake water, well water, and tap water.

[0018] Advantages of the present invention: The present invention overcomes the disadvantages of traditional detection methods such as being cumbersome and time-consuming, high cost, and complex sample processing. The novel electrochemical sensor based on the RE-MOF@C 60 / β-CD composite has been successfully used to detect Dcp in water bodies. This nanocomposite combines the host-guest recognition performance of β-CD with the excellent electrocatalytic activity of RE-MOF and the high electron transfer performance of C 60 . The synergistic effect enables the sensor to have rapid, sensitive, and selective detection of Dcp, with a wide detection range and a low detection limit. In addition, satisfactory recoveries were achieved when detecting Dcp in actual water samples including tap water and lake water, indicating the good applicability of this determination method. The present invention provides a new method for detecting Dcp and can be used as a potential method for monitoring other environmental pollutants. Brief Description of the Drawings

[0019] Figure 1 is a schematic diagram of the preparation and detection of an electrochemical sensor based on the RE-MOF@C 60 / β-CD composite.

[0020] Figure 2 is a result diagram of the material prepared by the method of Example 1. Among them, (A) is the X-ray photoelectron spectroscopy (XPS) diagram of the La-MOF@C 60 / β-CD material, and (B) is the Fourier transform infrared spectroscopy (FT-IR) diagram of C 60 , La-MOF, β-CD, and La-MOF@C 60 / β-CD.

[0021] Figure 3The bare glassy carbon electrode (GCE), β-CD / GCE, C 60 / GCE, La-MOF / GCE, and La-MOF@C 60 / β-CD / GCE cyclic voltammetry (CV) curves.

[0022] Figure 4 The result curves of the electrochemical sensor prepared by the method of Example 1 for detecting different concentrations of dichlorophenol standard solutions in tap water. Among them, (A) is the differential pulse voltammetry (DPV) curve, and (B) is the current-concentration linear fitting working curve.

[0023] Figure 5 The test results of the electrochemical sensor prepared by the method of Example 1. Among them, (A) is the reproducibility test graph, and (B) is the selectivity test bar graph.

[0024] Figure 6 The result curves of the electrochemical sensor prepared by the method of Example 2 for detecting different concentrations of dichlorophenol standard solutions in lake water. Among them, (A) is the differential pulse voltammetry (DPV) curve, and (B) is the current-concentration linear fitting working curve. Detailed implementation manners

[0025] The following further illustrates the detailed implementation manners of the present invention in combination with the attached drawings and technical solutions.

[0026] Example 1

[0027] An La-MOF@C 60 / β-CD / GCE sensor is applied to the detection of dichlorophenol in tap water, including the following steps:

[0028] 0.93 g of rare earth metal salt lanthanum nitrate and 1.55 g of organic ligand dimethylimidazole are respectively ultrasonically dissolved in 10 mL of methanol. 0.01 g of C 60 and 0.01 g of β-CD are mixed with the above two solutions and magnetically stirred for 30 minutes. Then it is transferred to a 25 mL reaction kettle and placed in an oven at 150 °C for reaction for 12 hours. After cooling, the product is centrifuged, washed 3 times with absolute ethanol, and then dried in an oven at 80 °C for 12 hours to obtain the La-MOF@C 60 / β-CD composite material.

[0029] Figure 2 A is the XPS measurement spectrum of the La-MOF@C 60 / β-CD composite material prepared by the method of Example 1. The characteristic peaks of C, N, O, and La elements are contained in the spectrum, indicating the successful synthesis of the composite material.

[0030] Figure 2B is C prepared by the method of Example 1 60 , La-MOF, β-CD and La-MOF@C 60 / β-CD's FT-IR, the composite material La-MOF@C 60 / β-CD's infrared spectrogram contains the characteristic peaks of individual C 60 , La-MOF, and β-CD materials, indicating the successful synthesis of this composite material.

[0031] Weigh the La-MOF@C 60 / β-CD composite material prepared by the method of Example 1 and ultrasonically disperse it evenly with DMF to obtain a dispersion. Before modifying the electrode, polish the glassy carbon electrode with 1.0μm and 0.05μm alumina powder respectively, and then ultrasonically clean it successively in water, ethanol and water. Drop the material dispersion on the surface of the polished glassy carbon electrode and dry it to obtain La-MOF@C 60 / β-CD / GCE. Prepare La-MOF / GCE, β-CD / GCE, C 60 / GCE and La-MOF@C 60 / GCE under the same conditions.

[0032] Connect the working electrode La-MOF@C 60 / β-CD / GCE prepared by the method of Example 1, the counter electrode platinum wire and the Ag / AgCl reference electrode to the electrochemical workstation and assemble them into an electrochemical sensor.

[0033] Use cyclic voltammetry (CV) to examine the electrocatalytic effect of bare glassy carbon electrode (GCE), β-CD / GCE, C 60 / GCE, La-MOF / GCE and La-MOF@C 60 / β-CD / GCE on 2,4-dichlorophenol in water. As Figure 3 shown, compared with other material-modified electrodes, the CV peak current of La-MOF@C 60 / β-CD / GCE is the largest and the effect is the best.

[0034] Figure 4 A, record the DPV curves of the electrochemical sensor prepared by the method of Example 1 for detecting different 2,4-dichlorophenol concentrations in tap water through the electrochemical workstation, read the current values corresponding to different 2,4-dichlorophenol concentrations, and draw the current-concentration linear fitting working curve as Figure 4 shown in B. The linear detection range is 0.03 μM - 25 μM, and the detection limit is 11.6 nM.

[0035] Figure 5 The La-MOF@C prepared by the method of Example 1 60Reproducibility (A) and selectivity (B) of the / β-CD / GCE for the detection of dichlorophenol. Ten parallel modified electrodes were used to detect 10 μM dichlorophenol. As shown by Figure 5 A, the relative standard deviation (RSD) of the DPV response current value was 3.49%, indicating that the sensor had good reproducibility. In addition, to evaluate the selectivity of the sensor, 10 μM Dcp was detected in tap water containing interfering substances such as structural analogs and inorganic ions. The effects of hydroquinone (HQ), 4-aminophenol (p-NP), resorcinol (RC), Na + , NH 4 + , K + , Mg 2+ , Cl - , SO 4 2- , and PO 4 3- on the DPV current of dichlorophenol (Dcp) were recorded, and it was found that all signals could remain above 90% after the addition of interfering substances, indicating that the La-MOF@C 60 / β-CD sensor had good selectivity.

[0036] The recoveries of the sensor in spiked tap water are shown in Table 1. The recoveries were between 96.6% and 102.6%, indicating the good applicability of the sensor in tap water.

[0037] Table 1 Recovery measurements of dichlorophenol in tap water samples

[0038]

[0039] Example 2

[0040] A method for detecting dichlorophenol in lake water using a La-MOF@C 60 / β-CD / GCE sensor includes the following steps:

[0041] Dissolve 0.93 g of rare earth metal salt lanthanum nitrate and 1.55 g of organic ligand dimethylimidazole in 10 mL of methanol by ultrasonic treatment respectively. Mix 0.01 g of C 60 and 0.01 g of β-CD with the above two solutions and stir magnetically for 30 minutes. Then transfer it to a 25 mL reaction kettle, place it in an oven at 150 °C and react for 12 hours. After cooling, centrifuge the product, wash it 3 times with absolute ethanol, and then dry it in an oven at 80 °C for 12 hours to obtain the La-MOF@C 60 / β-CD composite material.

[0042] Prepare the La-MOF@C 60The La-MOF@C / β-CD composite material and DMF were ultrasonically dispersed evenly to obtain a dispersion. Before modifying the electrode, the glassy carbon electrode was polished with 1.0 μm and 0.05 μm alumina powders respectively, and then ultrasonically cleaned successively in water, ethanol and water. The material dispersion was drop-coated on the surface of the polished glassy carbon electrode and dried to obtain La-MOF@C / β-CD / GCE. Under the same conditions, La-MOF / GCE, β-CD / GCE, C / GCE and La-MOF@C / GCE were prepared. 60 The working electrode La-MOF@C / β-CD / GCE prepared, the counter electrode platinum wire and the Ag / AgCl reference electrode were connected to an electrochemical workstation to assemble an electrochemical sensor. 60 / β-CD / GCE, the counter electrode platinum wire and the Ag / AgCl reference electrode were connected to an electrochemical workstation to assemble an electrochemical sensor. 60 / GCE.

[0043] The prepared working electrode La-MOF@C 60 / β-CD / GCE, the counter electrode platinum wire and the Ag / AgCl reference electrode were connected to an electrochemical workstation to assemble an electrochemical sensor.

[0044] The DPV curves of the electrochemical sensor for detecting different concentrations of dichlorophenol in lake water were recorded by the electrochemical workstation, the current values corresponding to different dichlorophenol concentrations were read, and the current-concentration linear fitting working curve as shown in Figure 6 was plotted. The linear detection range was obtained as 0.02 μM - 20 μM, and the detection limit was 8.6 nM.

[0045] The recovery rates of the sensor in tap water with added standard are shown in Table 2. The recovery rates are between 94.3% and 100%, indicating the good applicability of the sensor in lake water.

[0046] Table 2 Measurement of the recovery rate of dichlorophenol in lake water samples

[0047]

[0048] The description presented in the above exemplary embodiments is only used to illustrate the technical solutions of the present invention and is not intended to be exhaustive, nor is it intended to limit the present invention to the precise forms described. Obviously, many changes and variations are possible for those of ordinary skill in the art according to the above teachings. The exemplary embodiments are selected and described to explain the specific principles of the present invention and its practical applications, so that other technical personnel in the art can understand, implement and utilize various exemplary embodiments of the present invention and their various alternative forms and modified forms. The protection scope of the present invention is intended to be defined by the appended claims and their equivalent forms.

Claims

1. A RE-MOF@C for the detection of dichlorophenol in water 60 The method for preparing a / β-CD / GCE electrode is characterized in that: Here are the steps: (1)RE-MOF@C 60 Preparation of / β-CD composite materials: rare earth metal salt and organic ligand are ultrasonically dissolved in organic solvents to obtain two solutions; 60 , β-CD and the two solutions were mixed and magnetically stirred; after reacting for a certain time under certain temperature conditions, the reaction was cooled, the product was centrifuged and washed to obtain a precipitate, and then dried to obtain RE-MOF@C 60 / β-CD composites; (2) Preparation of electrochemical sensor: RE-MOF@C 60 The / β-CD composite material is ultrasonically dispersed uniformly with an organic solvent to obtain a dispersion; before modifying the glassy carbon electrode, the glassy carbon electrode is polished with alumina powders with a particle size of 1.0 μm and 0.05 μm, respectively, and then ultrasonically cleaned in water, ethanol and water in turn; the dispersion is droplet-coated on the polished surface of the glassy carbon electrode and dried to obtain RE-MOF@C 60 / β-CD / GCE electrode.

2. The preparation method according to claim 1, characterized in that: In step (1), the rare earth metal salt includes one or a mixture of two or more of rare earth metal nitrates and rare earth metal chlorides.

3. The preparation method according to claim 1, characterized in that: In step (1), the organic ligand includes one or a mixture of two or more of dimethylimidazole, terephthalic acid, aminoterephthalic acid, and dihydroxyterephthalic acid.

4. The preparation method according to claim 1, characterized in that: In steps (1) and (2), the organic solvent includes one or a mixture of two or more of methanol, ethanol, acetonitrile, dichloromethane, dimethyl sulfoxide, toluene, acetone, tetrahydrofuran, isopropanol, n-butanol, and N,N-dimethylformamide.

5. The preparation method according to claim 1, characterized in that: In step (1), the magnetic stirring time is 0.1 to 96 hours.

6. The preparation method according to claim 1, characterized in that: In step (1), the certain temperature is 60 to 250° C., and the certain time is 0.5 to 96 hours.

7. Application of the electrochemical sensor obtained by the preparation method according to any one of claims 1 to 6 for electrochemical detection of dichlorophenol in water, characterized in that: RE-MOF@C 60 / β-CD / GCE were connected to an electrochemical workstation as working electrode, counter electrode and reference electrode and assembled into an electrochemical sensor for electrochemical detection of dichlorophenol in water.

8. The use according to claim 7, characterized in that: The reference electrode is an Ag / AgCl electrode, a saturated calomel electrode or a mercury-mercurous sulfate electrode.

9. The use according to claim 7, characterized in that: The counter electrode comprises a platinum wire or platinum sheet electrode.

10. The use according to claim 7, characterized in that: The water bodies include river water, lake water, well water and tap water.

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