A glassy carbon electrode based on Cu-MOF@MnCO3 modification and its preparation method, and an electrochemical sensor.

Abstract

The application provides a Cu-MOF@MnCO3 modified glassy carbon electrode and a preparation method thereof and an electrochemical sensor, and the preparation method comprises the following steps: S1, preparing Cu-MOF@MnCO3 powder; S2, polishing, cleaning and drying the surface of a glassy carbon electrode for standby; S3, dissolving the Cu-MOF@MnCO3 powder in DMF, dropwise coating the surface of the glassy carbon electrode treated in the step S2, and heating and drying under an infrared lamp to obtain a Cu-MOF@MnCO3 modified glassy carbon electrode. On the one hand, by combining the signal generated by mercury ions itself and the internal reference signal generated when Cu 2+ and Cu + in the Cu-MOF occur a reduction reaction, the false positive phenomenon is effectively avoided, and the anti-interference, stability and reliability of the electrochemical sensor for detecting mercury ions are improved. On the other hand, the application can further widen the detection range of the electrochemical sensor and reduce the detection limit by amplifying the double signals of MnCO3, and is particularly suitable for detecting trace mercury ions.

Description

Technical Field

[0001] This invention relates to the field of mercury ion detection technology, specifically to a glassy carbon electrode based on Cu-MOF@MnCO3 modification, its preparation method, and an electrochemical sensor. Background Technology

[0002] Mercury ions are highly toxic heavy metal ions that pose a serious threat to the environment and human health. Due to their widespread presence in industrial wastewater, pesticide residues, and the natural environment, mercury pollution has received widespread global attention. Therefore, developing rapid, sensitive, and highly specific mercury ion detection technologies is particularly important. Traditional mercury ion detection methods include atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). While these methods offer high sensitivity and accuracy, they typically require complex sample pretreatment processes, expensive equipment, and specialized operators, making rapid on-site detection difficult.

[0003] With the development of technology, electrochemical detection technology has gradually become a research hotspot in the field of mercury ion detection due to its advantages such as low cost, portability, ease of operation, and real-time monitoring capabilities. Electrochemical sensors quantitatively analyze the presence of target substances, such as mercury ions, by measuring changes in electrical signals. These sensors typically consist of a working electrode, a reference electrode, and an auxiliary electrode. When mercury ions react with the surface of the working electrode, they trigger changes in current, voltage, or resistance, which are then detected. However, despite their excellent performance in mercury ion detection, electrochemical sensors are not without flaws. One significant drawback is the susceptibility to false positives. This is mainly because electrochemical sensors are also sensitive to certain interfering substances, which may generate similar signals on the electrodes, leading to erroneous detection results. Summary of the Invention

[0004] To address the issue of false positives in electrochemical sensors when detecting mercury ion content, this invention provides a glassy carbon electrode based on Cu-MOF@MnCO3 modification, its preparation method, and an electrochemical sensor. This sensor combines the signal generated by the mercury ions themselves with the Cu in Cu-MOF... 2+ Reduced to Cu + The generated internal reference signal effectively avoids false positives, thereby improving the anti-interference, stability and reliability of the electrochemical sensor for mercury ion detection.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A method for preparing a glassy carbon electrode based on Cu-MOF@MnCO3 modification includes the following steps:

[0007] S1. Preparation of Cu-MOF@MnCO3 powder

[0008] S1.1: At room temperature, 2-aminoterephthalic acid and CuNO3·3H2O were added to DMF, and after ultrasonic treatment, the mixture was transferred to a polytetrafluoroethylene reactor and allowed to stand at 90-100℃ for 24-26 hours. Then, the mixture was cooled to room temperature, centrifuged, and the precipitate was washed and dried to obtain Cu-MOF powder.

[0009] The molar ratio of 2-aminoterephthalic acid to CuNO3·3H2O is 2 to 4:5.

[0010] S1.2: Add Cu-MOF powder and an equal amount of MnCO3 powder from step S1.1 to DMF, sonicate and then centrifuge. Wash and vacuum dry the precipitate to obtain Cu-MOF@MnCO3 powder.

[0011] S2. Electrode Pretreatment

[0012] Take a glassy carbon electrode, grind and polish its surface, then clean the surface and dry it under an infrared lamp for later use.

[0013] S3. Electrode Modification

[0014] Cu-MOF@MnCO3 powder was added to DMF and ultrasonically treated to obtain a suspension. The suspension was then applied dropwise to the surface of the glassy carbon electrode treated in step S2 and dried under an infrared lamp to obtain a Cu-MOF@MnCO3 modified glassy carbon electrode.

[0015] Further, in step S1.1, the duration of the ultrasonic treatment is 3 to 7 minutes; the working parameters of the centrifugation are: rotation speed of 8000 to 9000 rpm, centrifugation time of 3 to 6 minutes; the detergent used is anhydrous ethanol; the drying temperature is 50 to 70°C, and the drying time is 18 to 20 hours.

[0016] Further, in step S1.2, the method for preparing the MnCO3 powder includes the following steps:

[0017] S1.2.1: Mix ethylene glycol and ultrapure water in a 1:1 ratio, add MnSO4 powder, and ultrasonically stir until completely dissolved to obtain a mixed solution;

[0018] S1.2.2: At room temperature, NaHCO3 solution is added dropwise to the mixed solution in step S1.2.1 and stirred continuously for 4-6 hours; then centrifugation is performed, and the precipitate is washed and vacuum dried to obtain MnCO3 powder.

[0019] Further, in step S1.2.2, the molar ratio of MnSO4 to NaHCO3 is 1:1 to 1.5.

[0020] Further, in step S1.2, the duration of ultrasonic treatment is 35-50 min; the working parameters of centrifugation are: rotation speed of 8000-9000 rpm, centrifugation time of 4-6 min; the detergent used is anhydrous ethanol; the vacuum drying temperature is 50-70℃, and the drying time is 10-14 h.

[0021] Further, in step S2, alumina powder with particle sizes of 0.3 μm and 0.05 μm is used to grind and polish the surface of the glassy carbon electrode in sequence; anhydrous ethanol and ultrapure water are used to clean the glassy carbon electrode after grinding and polishing.

[0022] Further, in step S3, the relationship between the amount of Cu-MOF@MnCO3 drop coating and the diameter of the glassy carbon electrode is 0.5 × 10⁻⁶. -3 ~1×10 -3 mg: 1 mm.

[0023] Furthermore, in step S3, the duration of the ultrasonic treatment is 20–40 minutes.

[0024] The glassy carbon electrode based on Cu-MOF@MnCO3 modification prepared by any of the above preparation methods.

[0025] An electrochemical sensor comprising the aforementioned glassy carbon electrode.

[0026] This invention uses Cu-MOF to provide an internal reference signal. The abundant metal ions inside Cu-MOF give it excellent electrochemical properties. During electrochemical detection, in addition to the signal that mercury ions themselves may generate, the Cu-MOF itself also provides an internal reference signal. 2+ A reduction reaction occurs, generating an internal control signal. This dual-signal phenomenon effectively avoids false positives. The ionic reactions involved in this process are as follows:

[0027] Hg 2+ +2e - →Hg (detection signal)

[0028] Cu 2+ +e - →Cu + (Internal reference signal)

[0029] The beneficial effects of this invention are as follows:

[0030] 1. This invention is based on Hg 2+ The reduction generates a detection signal, and Cu 2+The dual-signal mechanism that generates the internal reference signal is restored to effectively avoid false positives, prevent misjudgment, and improve the accuracy of detection.

[0031] 2. Cu in this invention 2+ Reduced to Cu + Part of Cu + Released into the electrolyte, it increases the number of holes on the surface of the sensing electrode, promoting the growth of Hg. 2+ The reduction reaction caused the detected Hg to... 2+ The signal peak increases, thereby achieving Hg 2+ The effect of signal amplification is detected. Simultaneously, when Hg in the electrolyte... 2+ When the content increases, more Hg 2+ This will lead to more Cu 2+ Reduced to Cu + And more Cu + This will further promote Hg 2+ The restoration makes it easier to detect, forming a positive feedback loop.

[0032] 3. The MnCO3 in this invention has a porous structure and good electrocatalytic activity, and is effective against Hg. 2+ The detection has a significant signal amplification effect, which can further broaden the detection range of electrochemical sensors and reduce the detection limit, making it particularly suitable for the detection of trace mercury ions.

[0033] 4. The MnCO3 in this invention has good biocompatibility and cycling stability, and can easily combine with Cu-MOF. Furthermore, the adsorption and polymerization of Cu-MOF and MnCO3 particles together, and the composite of the two porous particles, increases edge defects, providing more active sites for mercury ion attachment, which is more conducive to the redox reaction.

[0034] 5. This invention provides an electrochemical sensor for the ultrasensitive electrochemical detection of mercury ions, obtained by surface-modifying a glassy carbon electrode with Cu-MOF@MnCO3 as a modifier and DMF as a film-forming agent. The sensor exhibits a broad detection range and a low detection limit for mercury ions. Furthermore, this dual-signal electrochemical sensor demonstrates excellent anti-interference capabilities, reliability, repeatability, and applicability, enabling sensitive, accurate, and efficient analysis and detection of mercury ions in water. Attached Figure Description

[0035] Figure 1 The image shows the microstructure of the Cu-MOF@MnCO3 powder described in Example 1.

[0036] Figure 2 The XRD patterns of Cu-MOF@MnCO3 powder, Cu-MOF powder, and MnCO3 powder in Example 1 are shown.

[0037] Figure 3 The images show the FTIR spectra of Cu-MOF@MnCO3 powder, Cu-MOF powder, and MnCO3 powder from Example 1.

[0038] Figure 4 The flowchart shows the preparation and performance testing of the glassy carbon electrode based on Cu-MOF@MnCO3 modification as described in Example 1.

[0039] Figure 5 For different Hg in Example 1 2+ Linear relationship curves between DPV current signals of mercury ions and copper ions at different concentrations and mercury ion concentration.

[0040] Figure 6 a represents the bare glassy carbon electrode in Comparative Example 3, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+ A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5).

[0041] Figure 6 b represents the MnCO3-modified glassy carbon electrode from Comparative Example 2, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+ A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5).

[0042] Figure 6 c represents the Cu-MOF-modified glassy carbon electrode from Comparative Example 1, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+ A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5).

[0043] Figure 6 d represents the Cu-MOF@MnCO3 modified glassy carbon electrode from Example 1, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+ A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5). Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0045] Example 1

[0046] This embodiment describes a method for preparing a Cu-MOF@MnCO3 modified glassy carbon electrode, which includes the following steps:

[0047] S1. Preparation of Cu-MOF@MnCO3 powder

[0048] S1.1: At room temperature, 0.12 g of 2-aminoterephthalic acid and 0.25 g of CuNO3·3H2O were added to 10 mL of DMF. After ultrasonic treatment for 3–7 min, the mixture was transferred to a polytetrafluoroethylene reactor and allowed to stand at 100 °C for 25 h. Subsequently, the mixture was cooled to room temperature and centrifuged at 8000 rpm for 5 min. The precipitate was washed three times with anhydrous ethanol and dried at 60 °C to obtain Cu-MOF powder.

[0049] S1.2: Add 50 mg of Cu-MOF powder from step S1.1 and an equal amount of 50 mg of MnCO3 powder to DMF, sonicate for 40 min, centrifuge at 9000 rpm for 5 min, wash the precipitate with anhydrous ethanol, and vacuum dry at 60 °C for 12 h to obtain Cu-MOF@MnCO3 powder.

[0050] Microscopic morphology analysis:

[0051] The morphology of the Cu-MOF@MnCO3 powder prepared in this example was characterized and analyzed using field emission scanning electron microscopy (MIRA, TESCAN). Figure 1 The figure shows the microstructure of Cu-MOF@MnCO3 described in this embodiment. As shown, Cu-MOF and MnCO3 particles are adsorbed and polymerized together. The composite of the two porous particles increases the edge defects, providing more active sites for mercury ion attachment and making the redox reaction more favorable.

[0052] XRD analysis:

[0053] XRD was used to analyze the crystal phases of Cu-MOF@MnCO3 powder, Cu-MOF powder, and MnCO3 powder. Figure 2 The XRD patterns of Cu-MOF@MnCO3 powder, Cu-MOF powder, and MnCO3 powder in this embodiment are shown. The results show that in the XRD pattern of Cu-MOF@MnCO3 powder, characteristic diffraction peaks of Cu-MOF appear at 2θ = 28.8°, 14.96°, 16.9°, and 24.78°, and characteristic diffraction peaks of MnCO3 appear at 2θ = 24.25°, 31.36°, 37.52°, 41.42°, 45.19°, and 51.6°, proving that the crystal structures of both Cu-MOF and MnCO3 are preserved in Cu-MOF@MnCO3 powder.

[0054] FTIR analysis:

[0055] The crystal phase of Cu-MOF@MnCO3 powder was analyzed by FTIR. Figure 3 These are the FTIR spectra of Cu-MOF@MnCO3 powder, Cu-MOF powder, and MnCO3 powder in this embodiment. The results show that the FTIR spectrum of Cu-MOF@MnCO3 is at 3254 cm⁻¹. -1 1574cm -1 1369cm -1 764cm -1 A tensile vibration peak of Cu-MOF appeared at 1402 cm⁻¹. -1 3408cm -1 The appearance of the tensile vibration peak of MnCO3 further confirms the successful preparation of the Cu-MOF@MnCO3 powder in terms of crystal structure.

[0056] XPS Analysis:

[0057] Elemental valence state analysis of Cu-MOF@MnCO3 powder was performed using XPS. The results showed that peaks of C, O, N, Cu, and Mn, essential for the composition of Cu-MOF@MnCO3 composite materials, were present in the full spectrum. In the fine spectra of C, O, N, Cu, and Mn, deconvolution peaks corresponding to the chemical bonds between Cu-MOF and MnCO3 were observed, along with Cu... 2+ and Cu + The presence of two valence states demonstrates the successful preparation of the Cu-MOF@MnCO3 powder in terms of elemental composition.

[0058] S2. Electrode Pretreatment

[0059] A glassy carbon electrode with a diameter of 6 mm was taken, and its surface was polished sequentially with alumina powder with particle sizes of 0.3 μm and 0.05 μm to obtain a mirror-like surface. The glassy carbon electrode was then rinsed with anhydrous ethanol and ultrapure water, respectively, and dried under an infrared lamp for later use.

[0060] S3. Electrode Modification

[0061] 1.5 mg of Cu-MOF@MnCO3 powder was added to 1.5 mL of LDMF, and the mixture was sonicated for 40 min to obtain a suspension. 4 μL of this suspension was dropwise coated onto the surface of the glassy carbon electrode treated in step S1, and then dried under an infrared lamp to obtain a Cu-MOF@MnCO3 modified glassy carbon electrode. Figure 4 This is the preparation process and performance test diagram of the Cu-MOF@MnCO3 modified glassy carbon electrode described in this embodiment.

[0062] The method for preparing the MnCO3 powder used in step S1.2 above includes the following steps:

[0063] S1.2.1: Mix ethylene glycol and ultrapure water in a 1:1 ratio, add 2.3g of MnSO4 powder, and sonicate until completely dissolved to obtain a mixed solution.

[0064] S1.2.2: At room temperature, 110 mL of 150 mM NaHCO3 solution was added dropwise to the mixed solution in step S1.2.1, and the mixture was stirred continuously for 6 h. Then, the mixture was centrifuged at 11000 rpm for 12 min, the precipitate was washed with ultrapure water, and MnCO3 powder was obtained after vacuum drying at 70 °C for 13 h.

[0065] The Cu-MOF@MnCO3 modified glassy carbon electrode prepared in Example 1 was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the counter electrode. HAc-NaAc solution (pH = 4.5) was used as the buffer solution to test different concentrations (0.10, 0.15, 0.30, 0.60, 0.90, 1.20, 1.50, 2.00, and 2.50 μM) of Hg. 2+ The DPV current signal curves of mercury ions and copper ions were obtained through detection. The mercury ion concentration and the corresponding peak current values ​​of mercury ions and copper ions are recorded in Table 1. Figure 5 The curves show the linear relationship between the DPV current signals of mercury and copper ions and the concentration of mercury ions.

[0066] Table 1. Record of peak current values ​​of mercury and copper ions at different ion concentrations.

[0067]

[0068] As can be seen from Table 1, with Hg 2+ As the concentration of Cu increases, 2+ peak and Hg 2+ The peak value shows a linear increasing trend. Figure 5 For different Hg values ​​in this embodiment 2+ The linear relationship curves between the DPV current signals of mercury ions and copper ions at different concentrations and the mercury ion concentration are shown in the figure. This sensor detects Cu ions within a linear range of 0.10–2.50 μM. 2+ and Hg 2+ The linear response signal and the linear fitting equations are as follows: Mercury ion: y = 9.3152x + 0.6409, correlation coefficient R0 2 =0.9994, copper ions: y = 7.8386x + 23.6870, correlation coefficient R 2=0.9917, with a detection limit as low as 6.82 nM (S / N=3).

[0069] Anti-interference and stability testing:

[0070] The Cu-MOF@MnCO3 modified glassy carbon electrode prepared in Example 1 was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the counter electrode. HAc-NaAc solution (pH = 4.5) was used as the buffer solution to react with Hg... 2+ 10 times the concentration of Co 2+ Cu 2+ Fe 2+ Mn 2+ Ni 2+ Pb 2+ and Zn 2+ The presence of 10 μM Hg 2+ The solution was analyzed. The peak current values ​​of different interfering ions and their corresponding mercury and copper ions are recorded in Table 2. The presence of interfering metal ions affects the Cu... 2+ and Hg 2+ The peak current caused slight interference; however, the maximum deviation was less than 10%. This indicates that the sensor of the present invention has good anti-interference capability because Cu-MOF in Cu-MOF@MnCO3 is rich in -NH groups and Hg 2+ It is a soft metal that can form a very strong chelate with -NH groups, exhibiting a higher binding affinity for -NH groups than other metal ions. This results in the sensor's ability to detect Hg. 2+ The detection has good anti-interference ability.

[0071] Table 2. Record of peak current values ​​of mercury ion and copper ion under different interfering ions.

[0072]

[0073] Over a 7-day period, the Cu-MOF@MnCO3 modified glassy carbon electrode prepared in Example 1 was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the counter electrode. HAc-NaAc solution (pH = 4.5) was used as the buffer solution. The peak current values ​​of mercury and copper ions at different days are recorded in Table 3. On day 7, Cu... 2+ The peak current decreased by 29.06%, Hg 2+ The peak current decreased by 10.42%, indicating that the sensor can still retain more than 90% of the signal after 6 days of storage. This demonstrates that the glassy carbon electrode modified by Cu-MOF@MnCO3 has good storage stability.

[0074] Table 3. Record of peak current values ​​of mercury ions and copper ions at different storage days.

[0075]

[0076] Example 2

[0077] This embodiment describes a method for preparing a Cu-MOF@MnCO3 modified glassy carbon electrode, which includes the following steps:

[0078] S1. Preparation of Cu-MOF@MnCO3 powder

[0079] S1.1: At room temperature, 0.10 g of 2-aminoterephthalic acid and 0.20 g of CuNO3·3H2O were added to 10 mL of DMF. After sonication for 5 min, the mixture was transferred to a polytetrafluoroethylene reactor and allowed to stand at 100 °C for 24 h. Subsequently, the mixture was cooled to room temperature and centrifuged at 8000 rpm for 5 min. The precipitate was washed three times with anhydrous ethanol and dried at 60 °C to obtain Cu-MOF powder.

[0080] S1.2: Add 50 mg of Cu-MOF powder from step S1.1 and an equal amount of 50 mg of MnCO3 powder to DMF, sonicate for 40 min, centrifuge at 9000 rpm for 5 min, wash the precipitate with anhydrous ethanol, and vacuum dry at 60 °C for 12 h to obtain Cu-MOF@MnCO3 powder.

[0081] S2. Electrode Pretreatment

[0082] A glassy carbon electrode with a diameter of 6 mm was taken, and its surface was polished sequentially with alumina powder with particle sizes of 0.3 μm and 0.05 μm to obtain a mirror-like surface. The glassy carbon electrode was then rinsed with anhydrous ethanol and ultrapure water, respectively, and dried under an infrared lamp for later use.

[0083] S3. Electrode Modification

[0084] 1.5 mg of Cu-MOF@MnCO3 powder was added to 1.5 mL of LDMF and sonicated for 40 min to obtain a suspension. 4 μL of the suspension was dropwise coated onto the surface of the glassy carbon electrode treated in step S1 and dried under an infrared lamp to obtain a Cu-MOF@MnCO3 modified glassy carbon electrode.

[0085] The method for preparing the MnCO3 powder used in step S1.2 above includes the following steps:

[0086] S1.2.1: Mix ethylene glycol and ultrapure water in a 1:1 ratio, add 2.0 g of MnSO4 powder, and sonicate until completely dissolved to obtain a mixed solution.

[0087] S1.2.2: At room temperature, 100 mL of 150 mM NaHCO3 solution was added dropwise to the mixed solution in step S1.2.1, and the mixture was stirred continuously for 6 h. Then, the mixture was centrifuged at 10000 rpm for 12 min, the precipitate was washed with ultrapure water, and dried under vacuum at 70 °C for 13 h to obtain MnCO3 powder.

[0088] Comparative Example 1

[0089] To verify the effectiveness of MnCO3 powder, this comparative example only uses the Cu-MOF powder prepared in Example 1. Specifically, the preparation method of the Cu-MOF-modified glassy carbon electrode in this comparative example includes the following steps:

[0090] S1: Take a glassy carbon electrode with a diameter of 6 mm, and use alumina powder with a particle size of 0.3 μm and 0.05 μm to grind and polish the surface of the glassy carbon electrode in sequence to obtain a mirror-like surface. Then rinse the glassy carbon electrode with anhydrous ethanol and ultrapure water respectively, and heat and dry it under infrared lamp for later use.

[0091] S2: Add 1.5 mg of Cu-MOF powder to 1.5 mL of LDMF and sonicate for 40 min to obtain a suspension. Apply 4 μL of the suspension dropwise to the surface of the glassy carbon electrode treated in step S1 and heat and dry it under an infrared lamp to obtain a Cu-MOF modified glassy carbon electrode.

[0092] Comparative Example 2

[0093] To verify the effectiveness of Cu-MOF powder, this comparative example only uses the MnCO3 powder prepared in Example 1. Specifically, the preparation method of the glassy carbon electrode based on MnCO3 modification in this comparative example includes the following steps:

[0094] S1: Take a glassy carbon electrode with a diameter of 6 mm, and use alumina powder with a particle size of 0.3 μm and 0.05 μm to grind and polish the surface of the glassy carbon electrode in sequence to obtain a mirror-like surface. Then rinse the glassy carbon electrode with anhydrous ethanol and ultrapure water respectively, and heat and dry it under infrared lamp for later use.

[0095] S2: Add 1.5 mg of Cu-MOF powder to 1.5 mL of LDMF and sonicate for 40 min to obtain a suspension. Apply 4 μL of the suspension dropwise to the surface of the glassy carbon electrode treated in step S1 and heat and dry it under an infrared lamp to obtain a MnCO3-modified glassy carbon electrode.

[0096] Comparative Example 3

[0097] To verify the combined effect of Cu-MOF powder and MnCO3 powder, this comparative example does not use the aforementioned Cu-MOF powder and MnCO3 powder. Specifically, this comparative example uses a glassy carbon electrode with a diameter of 6 mm, and uses alumina powder with particle sizes of 0.3 μm and 0.05 μm to grind and polish the surface of the glassy carbon electrode in sequence to obtain a mirror-like surface. Then, the glassy carbon electrode is rinsed with anhydrous ethanol and ultrapure water respectively, and then heated and dried under an infrared lamp to obtain a bare glassy carbon electrode.

[0098] Electrochemical detection:

[0099] The Cu-MOF@MnCO3 modified glassy carbon electrode, Cu-MOF modified glassy carbon electrode, MnCO3 modified glassy carbon electrode, and bare glassy carbon electrode obtained in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were used as working electrodes, saturated calomel electrodes as reference electrodes, and platinum electrodes as counter electrodes, respectively, with 10 μM Hg. 2+ HAc-NaAc solution (pH=4.5), and Hg-free solution. 2+ Using HAc-NaAc solution (pH=4.5) as a buffer solution, a comparison graph of DPV current signals for mercury ions and copper ions was obtained. Figure 6 The glassy carbon electrodes in the four sets of experiments were used in a solution containing 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2 + A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5).

[0100] Figure 6 a represents the bare glassy carbon electrode in Comparative Example 3, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+ A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5), as shown in the figure. Figure 6 As shown in a, in the absence of Hg 2+ In the buffer solution containing Hg, GCE did not detect a response current peak, while in the buffer solution containing Hg 2+ In the buffer solution, GCE detected a response current peak between -0.2 and 0.4 V, confirming that the peak appearing at 0.2–0.4 V is Hg. 2+ The response current peak.

[0101] Figure 6 b represents the MnCO3-modified glassy carbon electrode from Comparative Example 2, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5), as shown in the figure. Figure 6 As shown in b, in the absence of Hg 2+ In the buffer solution, no response current peak was detected for MnCO3 / GCE, proving that MnCO3 has a positive effect on Hg. 2+ The detection has no interference effect in the presence of Hg. 2+ In the buffer solution, Hg was detected by MnCO3 / GCE. 2+ The peak response current was almost 8 times larger than that of the blank GCE. This demonstrates the effect of MnCO3 on Hg 2+ The detection has a signal amplification effect.

[0102] Figure 6 c represents the Cu-MOF-modified glassy carbon electrode from Comparative Example 1, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+ A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5), as shown in the figure. Figure 6 As shown in c, in the absence of Hg 2+ In the buffer solution, Cu-MOF / GCE detected Cu near a potential of 0V. 2+ The response current peak, which originates from Cu in Cu-MOF 2+ The reduction, in the presence of Hg 2+ In the buffer solution, Cu 2+ The peak value was significantly improved, and compared to the blank GCE, Hg 2+ The current response shows a slight increase of 1.5 times, which is due to the Hg 2+ During the detection process, Hg in the electrolyte 2+ The adsorbed and aggregated particles are located on the surface of Cu-MOF@MnCO3. The Cu-MOF@MnCO3 matrix contains Cu... 2+ Reduced to Cu + Part of Cu + Released into the electrolyte, it increases the number of holes on the surface of the sensing electrode, promoting the growth of Hg. 2+ The reduction reaction. When Hg in the electrolyte... 2+ When the content increases, it will also conversely promote the growth of Cu in the Cu-MOF@MnCO3 matrix. 2+ Reduced to Cu + This reaction.

[0103] Figure 6 d represents the Cu-MOF@MnCO3 modified glassy carbon electrode from Example 1, in the presence of 10 μM Hg. 2+ HAc-NaAc buffer (pH=4.5) and Hg-free buffer. 2+A comparison of DPV current signals in HAc-NaAc buffer (pH=4.5), as shown in the figure. Figure 6 As shown in d, in the absence of Hg 2+ Cu-MOF@MnCO3 / GCE detected Cu in the buffer solution. 2+ The peak current increased by 5 times compared to Cu-MOF / GCE, demonstrating that MnCO3 promotes Cu 2+ The reduction of Cu enhanced 2+ The signal intensity of the reduction reaction. And in the presence of Hg... 2+ In the buffer solution, Hg was detected by Cu-MOF@MnCO3 / GCE. 2+ The peak current of Cu-MOF@MnCO3 / GCE was not affected compared to that of MnCO3 / GCE, proving that Cu-MOF@MnCO3 / GCE can amplify Cu... 2+ While maintaining peak current, it retains the MnCO3-Hg... 2+ The detection signal is amplified.

[0104] In summary, the electrochemical sensor prepared by this invention exhibits good anti-interference and stability for the detection of mercury ions; under optimized testing conditions, it demonstrates high detection sensitivity, wide detection range, and low detection limit for mercury ions, showing promising application prospects in the field of mercury ion detection.

[0105] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a glassy carbon electrode based on Cu-MOF@MnCO3 modification, characterized in that, Includes the following steps: S1. Preparation of Cu-MOF@MnCO3 powder S1.1: At room temperature, 2-aminoterephthalic acid and CuNO3·3H2O were added to DMF, and after ultrasonic treatment, the mixture was transferred to a polytetrafluoroethylene reactor and allowed to stand at 90-100℃ for 24-26 hours. Then, the mixture was cooled to room temperature, centrifuged, and the precipitate was washed and dried to obtain Cu-MOF powder. The molar ratio of 2-aminoterephthalic acid to CuNO3·3H2O is 2 to 4:

5. S1.2: Add Cu-MOF powder and an equal amount of MnCO3 powder from step S1.1 to DMF, sonicate and then centrifuge. Wash and vacuum dry the precipitate to obtain Cu-MOF@MnCO3 powder. S2. Electrode Pretreatment Take a glassy carbon electrode, grind and polish its surface, then clean the surface and dry it under an infrared lamp for later use. S3. Electrode Modification Cu-MOF@MnCO3 powder was added to DMF and ultrasonically treated to obtain a suspension. The suspension was then applied dropwise to the surface of the glassy carbon electrode treated in step S2 and dried under an infrared lamp to obtain a Cu-MOF@MnCO3 modified glassy carbon electrode.

2. The preparation method according to claim 1, characterized in that, In step S1.1, the duration of ultrasonic treatment is 3 to 7 minutes; the operating parameters of centrifugation are: rotation speed of 8000 to 9000 rpm, centrifugation time of 3 to 6 minutes; the detergent used is anhydrous ethanol; the drying temperature is 50 to 70°C, and the drying time is 18 to 20 hours.

3. The preparation method according to claim 1, characterized in that, In step S1.2, the method for preparing the MnCO3 powder includes the following steps: S1.2.1: Mix ethylene glycol and ultrapure water in a 1:1 ratio, add MnSO4 powder, and ultrasonically stir until completely dissolved to obtain a mixed solution; S1.2.2: At room temperature, NaHCO3 solution is added dropwise to the mixed solution in step S1.2.1 and stirred continuously for 4-6 hours; then centrifugation is performed, and the precipitate is washed and vacuum dried to obtain MnCO3 powder.

4. The preparation method according to claim 1, characterized in that, In step S1.2.2, the molar ratio of MnSO4 to NaHCO3 is 1:1 to 1.

5.

5. The preparation method according to claim 1, characterized in that, In step S1.2, the duration of ultrasonic treatment is 35-50 min; the working parameters of centrifugation are: rotation speed of 8000-9000 rpm and centrifugation time of 4-6 min; the detergent used is anhydrous ethanol; the vacuum drying temperature is 50-70℃ and the drying time is 10-14 h.

6. The preparation method according to claim 1, characterized in that, In step S2, alumina powder with particle sizes of 0.3 μm and 0.05 μm is used to grind and polish the surface of the glassy carbon electrode in sequence; anhydrous ethanol and ultrapure water are used to clean the glassy carbon electrode after grinding and polishing.

7. The preparation method according to claim 1, characterized in that, In step S3, the coating amount of Cu-MOF@MnCO3 is related to the diameter of the glassy carbon electrode by 0.5 × 10⁻⁶. -3 ~1×10 -3 mg / 1mm.

8. The preparation method according to claim 1, characterized in that, In step S3, the duration of the ultrasonic treatment is 20 to 40 minutes.

9. A glassy carbon electrode based on Cu-MOF@MnCO3 modification prepared by any one of the preparation methods of claims 1 to 8.

10. An electrochemical sensor comprising the glassy carbon electrode of claim 9.

Images