Electrochemical sensor, preparation method thereof and application of electrochemical sensor in detection of microcystin-LR
By introducing an iron-aluminum bimetallic MOF and a graphene oxide modified layer into the electrochemical sensor, the sensitivity and selectivity problems of microcystin-LR detection were solved, and high-sensitivity and selective detection of microcystin-LR was achieved, which is suitable for the detection of microcystin-LR in freshwater systems.
Patent Information
- Application Number
- CN202510661243.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-22
- Publication Date
- 2025-09-05
AI Technical Summary
The existing microcystin-LR detection technology is not sensitive enough, making it difficult to achieve accurate quantification at low concentrations, and there is also a problem of insufficient detection selectivity.
An electrochemical sensor composed of an iron-aluminum bimetallic MOF and a graphene oxide modified layer was used to detect microcystin-LR by electrochemical impedance spectroscopy. The high catalytic activity and large surface area of the Fe/Al-MOF/GO material were combined with the electron transfer ability of graphene oxide to achieve specific binding and high-sensitivity detection.
It achieves high-sensitivity detection of microcystin-LR, can respond quickly at low concentrations, and has good selectivity and stability, making it suitable for accurate quantitative analysis in complex samples.
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Figure CN120594630A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electrochemical sensors, and in particular to an electrochemical sensor, a preparation method thereof, and application of the electrochemical sensor in detecting microcystin-LR. Background Art
[0002] Microcystin is a monocyclic peptide toxin produced by Microcystis aeruginosa in nutrient-rich aquatic environments. Among its various isomers, microcystin-LR (MC-LR) is particularly important due to its high toxicity and prevalence in harmful algal blooms (HABs). MC-LR is composed of five non-proteinogenic amino acids with leucine (L) and arginine (R) substituted at positions 2 and 4, respectively. It is considered the most toxic congener, LD 50 The concentration of MC-LR in freshwater systems is 43 μg / kg, and it is also classified as a Class 2B carcinogen. The widespread presence of MC-LR in freshwater systems poses a significant threat to the environment and public health. MC-LR has a strong tendency to bioaccumulate in aquatic organisms, and its toxicity increases as it moves up the food chain, ultimately affecting wildlife, livestock, and humans. Acute exposure to MC-LR can cause severe hepatotoxicity, while low-level chronic exposure may lead to tumorigenesis by disrupting cellular signaling pathways through the inhibition of PP1 and PP2A. In addition, MC-LR poisoning can manifest as symptoms with serious consequences ranging from headaches and abdominal pain to liver failure. This emphasizes the urgent need for effective monitoring and detection technologies, and therefore, the need to develop new, more sensitive sensors for microcystin detection. Summary of the Invention
[0003] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide an electrochemical sensor, a preparation method thereof, and an application thereof in detecting microcystin-LR.
[0004] The first object of the present invention is to provide an electrochemical sensor, which includes an electrode, on which a modified layer is provided; the modified layer includes an iron-aluminum bimetallic MOF and graphene oxide, and the iron-aluminum bimetallic MOF is in situ grown on the surface and between the layers of the graphene oxide.
[0005] A second object of the present invention is to provide a method for preparing an electrochemical sensor, comprising the following steps:
[0006] S1, mixing iron salt, aluminum salt and terephthalic acid and dissolving them in a solvent, adding graphene oxide to carry out hydrothermal reaction, centrifuging, washing and drying to obtain Fe / Al-MOF / GO material;
[0007] S2. Disperse the Fe / Al-MOF / GO material in a mixed solution of ethanol and water, add a binder and mix, then drop-coat the mixture on the surface of the electrode and dry it naturally to obtain an electrochemical sensor.
[0008] Furthermore, the molar ratio of the iron salt, the aluminum salt, and the terephthalic acid is 2-3:11-12:7-8; and the mass ratio of the terephthalic acid and the graphene oxide is 100-250:1-5.
[0009] Furthermore, the mass volume ratio of the Fe / Al-MOF / GO material to the mixed solution of ethanol and water is 0.1 mg-2 mg:1 mL; in the mixed solution of ethanol and water, the volume ratio of ethanol to water is 1-2:3.
[0010] Furthermore, the iron salt is ferric triacetylacetonate, and the aluminum salt is aluminum nitrate nonahydrate.
[0011] Furthermore, the hydrothermal reaction is performed at 120-140° C. for 24-50 hours.
[0012] Furthermore, the electrode is a glassy carbon electrode.
[0013] Furthermore, the solvent is a mixed solution of DMF and deionized water, and the volume ratio of DMF to deionized water is 15-20:40-55.
[0014] Furthermore, graphene oxide is prepared by the following method: placing graphite, sulfuric acid and sodium nitrate in an ice bath, heating, stirring until the oxidation reaction is complete, centrifuging, taking a solid precipitate, and drying the solid precipitate.
[0015] Furthermore, the adhesive is a perfluorosulfonic acid polymer, and the mass of the adhesive is 1 to 3% of the mass of the Fe / Al-MOF / GO material.
[0016] The third object of the present invention is to provide an application of the above-mentioned electrochemical sensor in detecting microcystin-LR.
[0017] Furthermore, the method for detecting microcystin-LR comprises the following steps:
[0018] Diluting a microcystin-LR standard with a buffer solution to obtain a plurality of standard solutions of different concentrations, respectively enriching the solutions on the modified layer of the electrochemical sensor, and performing electrochemical impedance spectroscopy to obtain electrochemical impedance spectroscopy curves;
[0019] A standard curve of microcystin-LR concentration-resistance value was constructed with the concentration of microcystin-LR as the horizontal axis and the resistance value in the electrochemical impedance spectroscopy as the vertical axis;
[0020] The sample to be tested is adsorbed by the modified layer of the electrochemical sensor and then subjected to electrochemical impedance spectroscopy to obtain a resistance value, and the resistance value corresponds to the microcystin-LR concentration-resistance standard curve to calculate the microcystin-LR concentration of the sample to be tested;
[0021] The electrochemical sensor is the electrochemical sensor according to any one of claims 1 to 2, or is prepared by the preparation method of the electrochemical sensor for detecting microcystin-LR according to any one of claims 3 to 8.
[0022] Furthermore, the resistance value is an average value obtained by three electrochemical impedance spectroscopy measurements.
[0023] Beneficial effects: The electrochemical sensor provided by the present invention is a bimetallic Fe / Al-MOF / GO non-enzymatic electrochemical impedance sensor for detecting MC-LR in algae powder samples using electrochemical impedance spectroscopy (EIS). Combining two metal ions into a single MOF structure can improve electrocatalytic activity, increase surface area and improve stability. Integrating graphene oxide into the Fe / Al-MOF matrix improves the transfer of electrons, and MC-LR can be quickly detected even at low concentrations. The specific binding interaction between microcystin-LR and the functional groups on the Fe / Al-MOF composite material, which is not affected by other substances, uses EIS as a detection method to further improve the sensitivity and selectivity of the sensor, achieving accurate quantification of MC-LR in algae powder samples. The innovative combination of bimetallic MOF, GO and EIS provides a practical and easy-to-use sensor for highly sensitive detection of microcystin-LR. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a scanning electron microscope image of aluminum iron terephthalate in the electrochemical sensor provided in Comparative Example 2 of the present invention;
[0025] Figure 2 This is a scanning electron microscope image of the modified layer material in the electrochemical sensor provided in Example 1 of the present invention;
[0026] Figure 3 A comparison of Fourier transform infrared spectra of three materials used in the electrochemical sensor provided in Example 1 of the present invention;
[0027] Figure 4 Schematic diagram of the principle of detecting microcystin-LR using the electrochemical sensor prepared in Example 1 of the present invention;
[0028] Figure 5 This is a linear relationship diagram of different concentrations of microcystin-LR obtained using the electrochemical sensor in Example 1 of the present invention;
[0029] Figure 6 This is a standard curve diagram between the concentration of microcystin-LR and the resistance value obtained by using the electrochemical sensor in Example 1 of the present invention;
[0030] Figure 7Electrochemical impedance spectroscopy of electrochemical sensors using materials with different modified layers to detect different concentrations of microcystin-LR;
[0031] Figure 8 Repeatability and reproducibility of the electrochemical sensor prepared in Example 1 of the present invention for detecting microcystin-LR;
[0032] Figure 9 The electrochemical impedance spectroscopy of Example 1, Comparative Example 1 and Comparative Example 2 and the unmodified glassy carbon electrode;
[0033] Figure 10 For the electrode prepared in Example 1, 10 -4 μg / ml of microcystin-LR and 10 -4 μg / ml of other common toxins and resistance values of compounds. DETAILED DESCRIPTION
[0034] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.
[0035] Example 1
[0036] The preparation method of graphene oxide comprises the following steps:
[0037] 2.0g of graphite, 80ml of concentrated sulfuric acid (98%), and 4.0g of sodium nitrate were placed in a three-necked flask, and 8.0g of potassium permanganate was slowly added in an ice bath. The mixture was completely cooled to below 10°C. The mixture was further magnetically stirred at 10°C for about 4 hours, and then the temperature was raised to 35°C for 4 hours. After that, 200ml of H2O was slowly added dropwise to the mixture, and the temperature of the reactants was maintained below 100°C. While mechanically stirring, 20ml of hydrogen peroxide was added to reduce the unreacted oxidant until the slurry turned golden yellow. The solid product was collected by centrifugation and washed several times with hydrochloric acid and deionized water. Finally, the product was vacuum dried at 60°C for 12 hours to obtain graphene oxide.
[0038] 4.22 g Al(NO3)3 9H2O and 0.79 g Fe(acac)3 were weighed and dissolved in a mixed solution of 10 mL ultrapure water and 27.5 mL DMF as solution A, 1.24 g H2BDC was dissolved in a solvent, and the solvent was a mixture of deionized water and DMF with a volume ratio of 20:55 as solution B. Solutions A and B were mixed and stirred, and 1.24 g terephthalic acid was added, and 0.005 g graphene oxide was added to obtain a mixture. The mixture was stirred and then added to a reactor containing polytetrafluoroethylene, heated in an oven at 130°C for 48 hours, cooled to room temperature, and a precipitate was obtained by centrifugation. It was washed three to five times with DMF and Et-OH, respectively, and then dried in a vacuum drying oven at 80°C for 12 hours to obtain a light yellow powdery solid, which is the material of the modified layer, Fe / Al-MOF / GO material.
[0039] 1 mg of the above-synthesized Fe / Al-MOF / GO material was added to 1 mL of a mixed solution of ethanol and water (volume ratio of 1:3), ultrasonicated for 1 min, and then 20 μL of perfluorosulfonic acid polymer was added and dispersed, and then drop-coated on the surface of the glassy carbon electrode and dried naturally to obtain an electrochemical sensor.
[0040] Example 2
[0041] When performing electrode modification, 2 mg of the above-synthesized Fe / Al-MOF / GO material was added to a 1 mL mixed solution of ethanol and water, ultrasonicated for 1 min, and then 20 μL of perfluorosulfonic acid polymer was added and dispersed, and then drop-coated on the surface of the glassy carbon electrode and dried naturally to obtain an electrochemical sensor.
[0042] Example 3
[0043] When performing electrode modification, 0.1 mg of the above-synthesized Fe / Al-MOF / GO material was added to a 1 mL mixed solution of ethanol and water, ultrasonicated for 1 min, and then 20 μL of perfluorosulfonic acid polymer was added and dispersed, and then drop-coated on the surface of the glassy carbon electrode and dried naturally to obtain an electrochemical sensor.
[0044] Comparative Example 1
[0045] 2.0g of graphite, 80ml of concentrated sulfuric acid (98%), and 4.0g of sodium nitrate were placed in a three-necked flask, and 8.0g of potassium permanganate was slowly added in an ice bath. The mixture was completely cooled to below 10°C. The mixture was further magnetically stirred at 10°C for about 4 hours, and then the temperature was raised to 35°C for 4 hours. After that, 200ml of H2O was slowly added dropwise to the mixture, and the temperature of the reactants was maintained below 100°C. While mechanically stirring, 20ml of hydrogen peroxide was added to reduce the unreacted oxidant until the slurry turned golden yellow. The solid product was collected by centrifugation and washed several times with hydrochloric acid and deionized water. Finally, the product was vacuum dried at 60°C for 12 hours to obtain graphene oxide.
[0046] 1 mg of the synthesized graphene oxide was added to 1 mL of a mixed solution of ethanol and water in a volume ratio of 1:3, and ultrasonicated for 1 min. 20 μL of a perfluorosulfonic acid polymer was then added and dispersed, and the mixture was drop-coated on the surface of a glassy carbon electrode and dried naturally to obtain an electrochemical sensor.
[0047] Comparative Example 2
[0048] 4.22 g of Al(NO3)3 9H2O and 0.79 g of Fe(acac)3 were weighed and dissolved in a mixed solution of 10 mL of ultrapure water and 27.5 mL of DMF as solution A. 1.24 g of H2BDC was dissolved in a solvent, and the solvent was a mixture of ultrapure water and DMF with a volume ratio of 20:55 as solution B. Solutions A and B were mixed and stirred, and then added to a reactor lined with polytetrafluoroethylene, and heated in an oven at 130°C for 48 h to obtain an iron-aluminum bimetallic MOF.
[0049] 1 mg of the synthesized iron-aluminum bimetallic MOF was added to a mixed solution of ethanol and water in a volume ratio of 1:3, ultrasonicated for 1 min, and then 20 μL of perfluorosulfonic acid polymer was added and dispersed, and then drop-coated on the surface of a glassy carbon electrode and dried naturally to obtain an electrochemical sensor.
[0050] Comparative Example 3
[0051] An electrochemical sensor was prepared using only a glassy carbon electrode without adding a modification layer. The remaining steps were the same as those in Example 1. The resistance value of the electrochemical sensor was measured.
[0052] The scanning electron microscope image of the aluminum ferrite terephthalate prepared in Comparative Example 2 is shown in the attached figure. Figure 1 As shown, this indicates that the crystal size of pure Fe / Al-MOF is about 2 μm and the nanomaterial has a rod-like structure.
[0053] The electron microscope scanning image of the modified layer material Fe / Al-MOF / GO material prepared in Example 1 is shown in the attached figure. Figure 2As shown: The combined nanomaterial has a rod-like structure and a typical wrinkled surface of graphene. Fe / Al-MOF grows in situ on the surface and interlayer of graphene oxide. Due to the van der Waals force between the sheet structures, graphene oxide enhances the aggregation and structural density of the composite material, thereby producing a high specific surface area and porosity.
[0054] Figure 3 The following is a comparison of the Fourier transform infrared spectra of the Fe / Al-MOF / GO material prepared in Example 1 of the present invention, the graphene oxide prepared in Comparative Example 1, and the Fe / Al-MOF prepared in Comparative Example 2. Figure 3 It can be seen that Example 1 successfully prepared Fe / Al-MOF / GO material.
[0055] Figure 4 Schematic diagram of the principle of detecting microcystin-LR by the electrochemical sensor prepared in Example 1 of the present invention.
[0056] Constructing electrochemical impedance spectroscopy of microcystin-LR
[0057] Microcystin-LR was diluted with a buffer solution to form standard solutions of different concentrations. The electrochemical sensor prepared in Example 1 was then placed in standard solutions of microcystin-LR of different concentrations. The solutions were mixed and adsorbed at room temperature, so that microcystin-LR was adsorbed on the electrochemical sensor. The sensor was then placed in an electrochemical detection cell and detected by electrochemical impedance spectroscopy. The electrochemical impedance spectra at different microcystin-LR concentrations were measured, and the resistance value of microcystin-LR was used as a direct response signal. Within the detection concentration range, the resistance value showed a standard linear relationship with the microcystin-LR concentration, thereby constructing a microcystin-LR electrochemical sensor.
[0058] As attached Figure 5 and attached Figure 6 As shown, the linear detection range of microcystin-LR concentration is 10 -5 ~10μg / mL, with the advantages of simple electrode modification and high sensitivity, the detection limit of microcystin-LR can reach 1.26×10 -5 μg / mL. As the concentration of microcystin-LR in the standard solution increases, it is more likely to bind to the bimetallic Fe / Al-MOF / GO and be trapped on the electrode surface. This leads to changes in the structure of Fe / Al-MOF / GO, making Fe(CN)6 3- / 4- The MC-LR can more freely reach the electrode surface, ultimately leading to a decrease in resistance. Therefore, the concentration of MC-LR can be indirectly detected through changes in electrochemical impedance spectroscopy. The MC-LR electrochemical sensor provided by the present invention can successfully detect low concentrations of MC-LR, with a wide linear range and a low detection limit.
[0059] Attachment Figure 7 Electrochemical impedance spectroscopy (EIS) was performed on microcystin-LR at different concentrations using the unmodified glassy carbon electrode and the electrode prepared in Example 1. Figure 7 As shown, the electrode prepared in Example 1 exhibited the lowest resistance in a high-concentration microcystin-LR solution, while the bare electrode exhibited the highest resistance. Electrochemical impedance spectroscopy (EIS) measurements of the electrode prepared in Example 1 in a buffer solution (0.1 M PBS) also revealed the highest resistance. Therefore, it can be concluded that the higher the concentration of microcystin-LR, the lower the resistance of the electrode prepared in Example 1.
[0060] Example 1, Comparative Example 1 and Comparative Example 2 and the unmodified glassy carbon electrode were subjected to the experiment in a solution containing 5 mmol / L Fe(CN)6 3- / 4- Electrochemical impedance spectroscopy was performed in 0.1 mol / L potassium chloride solution to test the electronic conductivity of different electrode surfaces. Figure 9 As shown in the figure, it can be seen that the electrode resistance prepared in Comparative Example 2 is the largest, while the electrode resistance of Example 1 prepared after introducing graphene oxide is the smallest. This is because graphene oxide enhances the transfer of electrons in the composite material.
[0061] Detection of Microcystin-LR in Freeze-dried Algae Powder
[0062] Microcystin-LR standard was added to the freeze-dried algae powder samples at concentrations of 0.1 μg / mL, 1 μg / mL, and 5 μg / mL. The samples were then filtered using a 0.22 μm filter membrane. Electrochemical impedance spectroscopy was performed using the electrochemical sensor prepared in Example 1 under the same conditions. The standard curve R ct =22.858×lg C+106.09(R 2 =0.989), the measured values at the three concentration levels were calculated to be (0.1±0.01)μg / mL, (1±0.22)μg / mL and (5±2.86)μg / mL, with an average recovery rate of 88.46%-101.81%. The results showed that within the linear range of 0.1-5μg / mL, the resistance value (R ct ) showed a good correlation with the MC-LR concentration; the recovery rate of this method for microcystin-LR in complex matrix (algae powder) met the detection requirements; the Fe / Al-MOF / GO / GCE prepared in Example 1 had a high sensitivity to electrochemical impedance spectroscopy detection of microcystin-LR.
[0063] Note: All tests were completed at room temperature (25±2°C), and each concentration was measured in parallel n=3 times.
[0064] Repeatability and reproducibility testing
[0065] Seven electrodes were prepared by the method of Example 1. -3 The electrochemical impedance spectroscopy was performed on the microcystin-LR at a concentration of μg / ml. Figure 8 As shown in (A), the average resistance is (179.6±2.8)Ω and the RSD is 0.72%, indicating that the electrochemical sensor prepared in Example 1 has good repeatability. -3 The reproducibility of the sensor was studied by measuring the concentration of microcystin-LR in the sample 7 times. Figure 8 As shown in (B), it shows that the sensor prepared in Example 1 has good reproducibility.
[0066] Note: All tests were completed at room temperature (25±2℃). Each electrode was measured in parallel n=3 times in the repeatability test.
[0067] Specificity test
[0068] Figure 10 For the electrode prepared in Example 1, 10 -4 μg / ml of microcystin-LR and 10 -4 The resistance values of other common toxins and compounds at 50 μg / ml, including microcystin-RR (MC-RR), domoic acid (DA), okadaic acid (OA), sodium chloride (NaCl), magnesium chloride (MgCl2), copper sulfate (CuSO4), potassium nitrate (KNO3), and mixed samples, were also analyzed. The results show that the resistance values of other toxins and compounds are higher than those of microcystin-LR, while the mixed sample does not show a significant resistance change. This selectivity can be attributed to the specific binding interaction between microcystin-LR and the functional groups on the Fe / Al-MOF composite material, which is unaffected by other substances.
[0069] Note: All tests were performed at room temperature (25±2°C) and repeated measurements were performed 3 times.
[0070] Any matters not mentioned above shall be subject to the existing technology.
[0071] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.
Claims
1. An electrochemical sensor, characterized in that The electrochemical sensor comprises an electrode, on which a modification layer is provided; the modification layer comprises an iron-aluminum bimetallic MOF and graphene oxide, and the iron-aluminum bimetallic MOF is in-situ grown on the surface and between layers of the graphene oxide.
2. A method for preparing an electrochemical sensor according to claim 1, characterized in that: The following steps are involved: S1, mixing iron salt, aluminum salt and terephthalic acid and dissolving them in a solvent, adding graphene oxide to carry out hydrothermal reaction, centrifuging, washing and drying to obtain Fe / Al-MOF / GO material; S2. Disperse the Fe / Al-MOF / GO material in a mixed solution of ethanol and water, add a binder and mix, then drop-coat the mixture on the surface of the electrode and dry it naturally to obtain an electrochemical sensor.
3. The preparation method according to claim 2, wherein The molar ratio of the iron salt, the aluminum salt and the terephthalic acid is 2-3:11-12:7-8; the mass ratio of the terephthalic acid and the graphene oxide is 100-250:1-5.
4. The preparation method according to claim 2, wherein The mass volume ratio of Fe / Al-MOF / GO material to the mixed solution of ethanol and water is 0.1 mg-2 mg:1 mL; in the mixed solution of ethanol and water, the volume ratio of ethanol to water is 1-2:
3.
5. The preparation method according to claim 2, wherein The iron salt is ferric triacetylacetonate, and the aluminum salt is aluminum nitrate nonahydrate.
6. The preparation method according to claim 2, wherein The hydrothermal reaction is carried out at 120-140° C. for 24-50 hours.
7. The preparation method according to claim 1, wherein The electrode is a glassy carbon electrode.
8. The preparation method according to claim 2, wherein The solvent is a mixed solution of DMF and deionized water, and the volume ratio of DMF to deionized water is 15-20:40-55; Graphene oxide is prepared by the following method: placing graphite, sulfuric acid and sodium nitrate in an ice bath, heating, stirring until the oxidation reaction is complete, centrifuging, taking a solid precipitate, and drying the solid precipitate; The adhesive is a perfluorosulfonic acid polymer, and the mass of the adhesive is 1-3% of the mass of the Fe / Al-MOF / GO material.
9. Use of the electrochemical sensor according to claim 1 in detecting microcystin-LR.
10. The use according to claim 9, characterized in that The method for detecting microcystin-LR comprises the following steps: Diluting a microcystin-LR standard with a buffer solution to obtain a plurality of standard solutions of different concentrations, respectively enriching the solutions on the modified layer of the electrochemical sensor, and performing electrochemical impedance spectroscopy to obtain electrochemical impedance spectroscopy curves; A standard curve of microcystin-LR concentration-resistance value was constructed with the concentration of microcystin-LR as the horizontal axis and the resistance value in the electrochemical impedance spectroscopy as the vertical axis; The sample to be tested is adsorbed by the modified layer of the electrochemical sensor and then subjected to electrochemical impedance spectroscopy to obtain a resistance value. The resistance value corresponds to the microcystin-LR concentration-resistance standard curve to calculate the microcystin-LR concentration of the sample to be tested.