Nickel-based 5-HT electrochemical sensor using dithiene-transition metal MOFs / MWCNTs / GCE
An electrochemical sensor, NiZn-MOF/MWCNTs/GCE, was prepared by compositing NiZn-MOF with MWCNTs. This solved the problem of poor conductivity of NiZn-MOF and enabled the detection of 5-HT with high sensitivity and high catalytic activity, exhibiting good detection linearity and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHWEST NORMAL UNIVERSITY
- Filing Date
- 2023-05-05
- Publication Date
- 2026-06-30
AI Technical Summary
In existing technologies, NiZn-MOF has poor conductivity, resulting in low electrocatalytic activity and low sensitivity during 5-HT detection.
A Ni Zn-MOF/MWCNTs/GCE electrochemical sensor was formed by combining Ni Zn-MOF with multi-walled carbon nanotubes (MWCNTs). The excellent conductivity of MWCNTs compensates for the insufficient conductivity of Ni Zn-MOF, and they are uniformly dispersed through π-π interactions, increasing the specific surface area and conductivity, providing more active sites, and promoting electron transfer and catalytic activity.
It improves the electrocatalytic activity and sensitivity of 5-HT detection, with a linear range of 0.5–150 μM and a detection limit of 0.03 μM, and has good reproducibility and anti-interference ability.
Smart Images
Figure CN116359302B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical sensor technology and relates to a 5-HT electrochemical sensor based on nickel dithionene-transition metal MOFs / MWCNTs / GCE. Background Technology
[0002] Serotonin (5-hydroxytryptamine, 5-HT) is a biological monoamine neurotransmitter and neuromodulator widely distributed in the central nervous system (CNS), peripheral nervous system, gastrointestinal tract (GI), and platelets. It plays a crucial role, along with other neurotransmitters, in various physiological functions and psychopathological processes, including thermoregulation, muscle contraction, cardiovascular function, endocrine regulation, and obsessive-compulsive disorder. Fluctuations in serotonin levels within the body, or levels exceeding certain ranges, can lead to physiological problems and are associated with various diseases. Therefore, accurate detection of 5-HT is of great significance for healthcare and clinical treatment.
[0003] Metal-organic frameworks (MOFs) are crystalline molecular materials with unique physicochemical properties and permanent internal pores. MOFs are widely used in adsorption, catalysis, gas storage, gas separation, drug delivery, luminescence, and sensing. Metal bis(dithione) complexes can be considered inorganic analogs of corresponding tetrathione-fulvalene (TTF) type donors, where the metal replaces the central C=C bond. Similar to TTFs and their derivatives, they also exhibit high redox activity and favorable solid-state interactions. Introducing inorganic ligand analogs to replace purely organic ligands endows frameworks with a range of additional multifunctional properties. However, the poor conductivity of standalone MOFs limits their application in electrochemical sensing. Many methods have been employed to address this issue in the prior art. A common approach is to combine MOFs with other conductive materials to form composite nanomaterials.
[0004] Electrochemical sensors have attracted increasing attention due to their rapid response, good portability, low cost, and high sensitivity. However, NiZn-MOF in existing technologies has poor conductivity, resulting in low electrocatalytic activity and low sensitivity in 5-HT detection. Summary of the Invention
[0005] This invention provides a nickel-based dithionene-transition metal MOFs / MWCNTs / GCE 5-HT electrochemical sensor, which can effectively solve the problems of low electrocatalytic activity and low sensitivity in the 5-HT detection process.
[0006] This invention discloses a nickel-based dithionene-transition metal MOFs / MWCNTs / GCE 5-HT electrochemical sensor, comprising a working electrode, a reference electrode, a counter electrode, and a buffer solution. The linear range of this electrochemical sensor is 0.5–150 μM, and the limit of detection (LOD) is 0.03 μM (S / N = 3).
[0007] Preparation of the working electrode in the 5-HT electrochemical sensor of this invention:
[0008] 1) Preparation of [Ni(C2S2(C6H4COOCH3)2)2]:
[0009] According to the ratio of 4.5 mmol of P2S5, 1.5 mmol of NiCl2·6H2O, and 20 mL of dioxane required for 3 mmol of dimethyl 4,4'-(2-hydroxyacetyl)benzoate, 4,4'-(2-hydroxyacetyl)benzoate, P2S5, NiCl2·6H2O, and dioxane were prepared. The 4,4'-(2-hydroxyacetyl)benzoate and P2S5 were refluxed in dioxane at 90 °C for 12 h. After cooling to room temperature, the mixture was filtered to remove excess P2S5, and the filtrate was obtained.
[0010] NiCl2·6H2O was dissolved in distilled water at a ratio of 1.5 mmol of NiCl2·6H2O to 5 ml of distilled water to obtain a NiCl2 solution.
[0011] Add NiCl2 solution to the filtrate, reflux at 82 °C for 2 hours, concentrate, cool in an ice-water bath, filter and collect the residue, wash the residue with minimal amounts of dioxane, water, ethanol and diethyl ether respectively, and dry to obtain [Ni(C2S2(C6H4COOCH3)2)2];
[0012] 2) Preparation of [Ni(C2S2(C6H4COOH)2)2]:
[0013] Based on the ratio of 30 mL of tetrahydrofuran (THF) and 10 mmol of KOH required for 1 mmol of [Ni(C2S2(C6H4COOCH3)2)2], take [Ni(C2S2(C6H4COOCH3)2)2], tetrahydrofuran and KOH respectively;
[0014] Dissolve KOH in water at a ratio of 10 mmol of KOH to 10 mL of water to obtain a KOH solution.
[0015] [Ni(C2S2(C6H4COOCH3)2)2] was dissolved in tetrahydrofuran, and then KOH solution was added. The mixture was stirred and refluxed at 60 °C for 10 hours. After cooling to room temperature, the mixture was concentrated. The resulting product was completely dissolved in water and filtered. The pH of the filtrate was adjusted to 6 with 1 M HCl to obtain a large amount of dark green solid. The solid was washed with water and dried to obtain [Ni(C2S2(C6H4COOH)2)2].
[0016] 3) Preparation of NiZn-MOF:
[0017] Take water and anhydrous ethanol separately in a volume ratio of 1:1, dissolve the anhydrous ethanol in water to obtain the first solvent;
[0018] N,N-dimethylformamide and anhydrous ethanol were taken in a volume ratio of 3:1. N,N-dimethylformamide was dissolved in anhydrous ethanol to obtain a second solvent.
[0019] According to the ratio of 0.096 mmol Zn(NO3)2·4H2O to 0.014 mmol [Ni(C2S2(C6H4COOH)2)2], 5.08 mL of the first solvent, and 0.52 mL of the second solvent, Zn(NO3)2·4H2O, [Ni(C2S2(C6H4COOH)2)2], the first solvent, and the second solvent were prepared respectively. Zn(NO3)2·4H2O was dissolved in the first solvent to obtain the first solution, and [Ni(C2S2(C6H4COOH)2)2] was dissolved in the second solvent to obtain the second solution. The first solution was added to the second solution, and after ultrasonic mixing, the mixture was kept at 80°C for 24 hours. Then, the mixture was cooled to room temperature at a cooling rate of 5°C / s, filtered, and the product was washed with ethanol to obtain NiZn-MOF.
[0020] 4) Preparation of NiZn-MOF / MWCNTs:
[0021] According to the ratio of 30 mg of carboxylated carbon nanotubes and 10 mg of NiZn-MOF added to 10 mL of N,N-dimethylformamide (DMF), N,N-dimethylformamide, carboxylated carbon nanotubes and Ni Zn-MOF were respectively taken, and the carboxylated carbon nanotubes and Ni Zn-MOF were added to DMF, ultrasonically dispersed for 2 h, and dried to obtain Ni Zn-MOF / MWCNTs;
[0022] Preparation of carboxylated carbon nanotubes: HNO3 with a volume ratio of 1:3 and H2SO4 with a volume molar concentration of 4.0 mol / L were mixed to form an acid solution. Carbon nanotubes (MWCNTs) were added to the acid solution at a ratio of 100 mg per 20 mL of acid solution. The solution was then vigorously magnetically stirred at room temperature for 18 h to obtain carboxylated carbon nanotubes (MWCNT-COOH).
[0023] 5) Preparation of the working electrode:
[0024] Ni Zn-MOF / MWCNTs were dispersed in DMF and ultrasonicated to obtain a dispersion. The dispersion was then dropped onto a treated glassy carbon electrode and dried under infrared light to obtain the working electrode.
[0025] Treatment of glassy carbon electrode (GCE): The glassy carbon electrode is polished with Al2O3 powder, then ultrasonically washed with ethanol and ultrapure water respectively, and dried under infrared lamp to obtain the treated glassy carbon electrode.
[0026] NiZn-MOF and multi-walled carbon nanotubes (MWCNTs) were ultrasonically mixed, and the excellent conductivity of MWCNTs compensated for the poor conductivity of NiZn-MOF.
[0027] This invention presents a 5-HT electrochemical sensor that combines redox-active three-dimensional MOFs [Zn2{Ni(C2S2(C6H4COO)2)2}(H2O)2]·2DMF with MWCNTs. The prepared Ni Zn-MOF / MWCNTs / GCE electrochemical sensor can be used for 5-HT detection. The nickel-zinc bis(dithione) metal-organic framework contains [NiS4] centers, multiple valence states of nickel-zinc bimetallic ions, and the p-electron system of benzene, which lowers the activation energy for charge transfer between different valence states, promotes the internal electron transfer rate, and enhances catalytic performance. Multi-walled carbon nanotubes (MWCNTs) have good conductivity and can be loaded onto Ni Zn-MOF through π-π interactions, allowing the slightly soluble Ni Zn-MOF to be uniformly dispersed in DMF, increasing the specific surface area and conductivity while reducing the aggregation of MWCNTs. Through synergistic effects, a large number of active sites are provided for redox reactions, promoting electron transfer on the electrode, reducing electrochemical impedance, increasing electrochemical specific surface area, and improving catalytic activity. Under optimized conditions, the sensor can detect 5-HT concentrations in the range of 0.5–150 μM, with a detection limit (LOD) of 0.03 μM (S / N = 3). Attached Figure Description
[0028] Figure 1 To prepare a solution containing 0.1 M KCl and 1.0 mM [Fe(CN)6]3- / 4- Cyclic voltammetry (CV) curves of bare GCE, NiZn-MOF / GCE, MWCNTs / GCE and NiZn-MOF / MWCNTs / GCE in buffer solutions.
[0029] Figure 2 To prepare a solution containing 0.1 M KCl and 5.0 mM [Fe(CN)6] 3- / 4- Impedance diagrams of bare GCE, Ni Zn-MOF / GCE, MWCNTs / GCE and Ni Zn-MOF / MWCNTs / GCE in buffer solutions.
[0030] Figure 3 This is a DPV diagram of the 5-HT electrochemical sensor of the present invention in 0.1M Tris-HCl buffer at different pH values.
[0031] Figure 4 The image shows the CV curves of the electrochemical sensor of this invention detecting 5-HT (1 mM) at different scan rates (20-100 mV / s) in 0.1M Tris-HCl buffer at pH 8.0.
[0032] Figure 5 The image shows the DPV detection of different concentrations of 5-HT by the electrochemical sensor of this invention in 0.1M Tris-HCl buffer at pH 8.0.
[0033] Figure 6 yes Figure 5 The graph shows the linear relationship between peak current and 5-HT concentration when performing DPV detection with different concentrations of 5-HT.
[0034] Figure 7 The stability test diagram shows the detection of 5-HT by a sensor prepared with five NiZn-MOF / MWCNTs modified electrodes in 0.1M Tris-HCl buffer containing 50 μM 5-HT at pH 8.0.
[0035] Figure 8 The modified electrode was stored for 7 days in 0.1 M Tris-HCl buffer containing 50 μM 5-HT at pH 8.0, and the same concentration of 5-HT was measured daily using the modified electrode.
[0036] Figure 9 To verify the anti-interference capability of this sensor, a 100 μM concentration of various interfering substances was added to a 0.1 M Tris-HCl buffer containing 10 μM 5-HT at pH 8.0, and the change in peak current was detected by DPV technology. Detailed Implementation
[0037] The present invention will now be clearly and completely described in conjunction with the accompanying drawings and specific embodiments. Example
[0038] 3 mmol of dimethyl 4,4'-(2-hydroxyacetyl)dibenzoate (0.98 g) and 4.5 mmol of P2S5 (1.0 g) were refluxed in 20 ml of dioxane at 90 °C for 12 hours. After cooling to room temperature, the mixture was filtered to remove excess P2S5, yielding a filtrate. 1.5 mmol of NiCl2·6H2O (0.36 g) was dissolved in 5 ml of distilled water to obtain a NiCl2 solution. The NiCl2 solution was added to the filtrate, and the mixture was refluxed at 82 °C for 2 hours. The solution was concentrated to remove the solvent, cooled in an ice-water bath, filtered, and the residue was collected. The residue was washed with a minimum amount of dioxane, water, ethanol, and diethyl ether, and dried to obtain [Ni(C2S2(C6H4COOCH3)2)2].
[0039] 10 mmol of KOH (0.56 g) was dissolved in 10 mL of water to obtain a KOH solution; 1 mmol of [Ni(C2S2(C6H4COOCH3)2)2] (0.78 g) was dissolved in 30 mL of tetrahydrofuran, and then the KOH solution was added. The mixture was stirred and refluxed at 60 °C for 10 hours. After cooling to room temperature, the mixture was concentrated to remove the solvent. The resulting product was completely dissolved in water and filtered to obtain the filtrate. The pH of the filtrate was adjusted to 6 with 1 M HCl to obtain a large amount of dark green solid. The solid was washed three times with water and dried to obtain [Ni(C2S2(C6H4COOH)2)2].
[0040] Anhydrous ethanol was dissolved in water at a volume ratio of 1:1 to obtain the first solvent; DMF was dissolved in anhydrous ethanol at a volume ratio of 3:1 to obtain the second solvent; 0.096 mmol (0.0236 g) Zn(NO3)2·4H2O was dissolved in 5.08 mL of the first solvent to obtain the first solution. 0.014 mmol (0.01 g) [Ni(C2S2(C6H4COOH)2)2] was dissolved in 0.52 mL of the second solvent to obtain the second solution. The first solution was added to the second solution in a 10 mL vial, and the mixture was ultrasonically mixed to obtain a dark green solution. The solution was kept at 80 °C for 24 hours, then cooled to room temperature at a cooling rate of 5 °C / s, filtered, and black needle-like crystals were obtained. The crystals were washed three times with EtOH to obtain NiZn-MOF.
[0041] Mix HNO3 with a volume ratio of 1:3 (4.0 mol / L) and H2SO4 with a volume ratio of 10.0 mol / L to form an acid solution. Add 100 mg of MWCNT to 20 mL of the acid solution and stir vigorously with a magnetic stirrer at room temperature for 18 h to obtain MWCNT–COOH.
[0042] 30 mg of carboxylated MWCNTs and 10 mg of Ni Zn-MOF were added to 10 mL of DMF, ultrasonically dispersed for 2 h, and dried to obtain Ni Zn-MOF / MWCNTs;
[0043] 1 mg of NiZn-MOF / MWCNTs was added to 1 ml of DMF and ultrasonically dispersed for 10 min to obtain the first dispersion. The GCE was polished with Al2O3 slurry with a concentration of 0.05 μm, dried under a nitrogen atmosphere, and then ultrasonicated in an ethanol-water solution for 3 min to obtain the treated GCE. 5 μL of the first dispersion was dropped onto the treated GCE and dried under infrared light to obtain the first working electrode.
[0044] 1 mg NiZn-MOF was added to 1 ml DMF and ultrasonically dispersed for 10 min to obtain a second dispersion. The GCE was polished with 0.05 μm Al2O3 slurry, dried under a nitrogen atmosphere, and then ultrasonicated in an ethanol-water solution for 3 min to obtain a treated GCE. 5 μL of the second dispersion was dropped onto the treated GCE and dried under infrared light to obtain the second working electrode.
[0045] The GCE was polished with a 0.05 μm Al₂O₃ slurry, dried under a nitrogen atmosphere, and then sonicated in an ethanol-water solution for 3 min to obtain the treated GCE. 1 mg of MWCNTs was added to 1 ml of DMF and sonicated for 10 min to obtain the third dispersion. 5 μL of the third dispersion was dropped onto the treated GCE and dried under infrared light to obtain the third working electrode.
[0046] GCE was polished with Al2O3 slurry with a concentration of 0.05 μm, dried under a nitrogen atmosphere, and then sonicated in an ethanol aqueous solution for 3 min to obtain bare GCE.
[0047] contrast:
[0048] The first, second, and third working electrodes, along with bare GCE, were used as working electrodes in a solution containing 0.1 M KCl and 1.0 mM [Fe(CN)6]. 3- / 4- CV tests were performed in the buffer solutions respectively to obtain... Figure 1 The cyclic voltammetry (CV) curves of the modified electrode are shown. From... Figure 1It can be seen that among the four modified electrodes, the second working electrode modified with Ni Zn-MOF has the worst conductivity, while the peak current of the first working electrode modified with Ni Zn-MOF / MWCNTs is significantly increased and higher than that of the other modified electrodes. This indicates a synergistic effect between Ni Zn-MOF and MWCNTs. This proves that the Ni Zn-MOF / MWCNTs electrode has been successfully modified.
[0049] The four modified electrodes were prepared with 0.1 M KCl and 5.0 mM [Fe(CN)6]. 3- / 4- Impedance curves in buffer solutions, such as Figure 2 . Figure 2 Display, MWCNTs / GCE, Ni Zn-MOF / MWCNTs / GCE ( Figure 2 a) and Ni Zn-MOF / GCE ( Figure 2 The Rct values of b) are all lower than those of bare GCE, and the Rct of NiZn-MOF / MWCNTs / GCE is significantly lower than that of the bare electrode. Through layer-by-layer modification of the bare GCE, the Rct value gradually decreases, and the Rct of NiZn-MOF / MWCNTs is significantly lower than that of the bare electrode, indicating that the charge transfer rate of the nanoprobe is higher than that of the bare electrode. These changes are related to... Figure 1 The results of the CV curves are consistent, further proving that the NiZn-MOF / MWCNTs electrode has been successfully modified.
[0050] The DPV diagrams of the 5-HT electrochemical sensor of this invention in 0.1M Tris-HCl buffer at different pH values are shown below. Figure 3 As shown, different pH values affect the current response and peak potential, with the best current response observed at pH=8.0. At pH=8.0, the modified electrode exhibits the best selective adsorption for 5-HT.
[0051] The electrochemical sensor of this invention detects 5-HT (1 mM) in 0.1 M Tris-HCl buffer at pH 8.0, and the CV curves are shown below at different scan rates (20-150 mV / s). Figure 4 As shown, in 0.1M Tris-HCl buffer at pH 8.0, the current response increases with increasing scan rate. Figure 4 In the lower half of the curve bundle, the scanning rate corresponding to the height position of each curve increases sequentially along the direction of the arrows in the figure. Figure 4 The scanning rate corresponding to the height position of each curve in the upper half of the curve bundle increases sequentially in the opposite direction of the arrows in the figure. The higher the scanning rate, the better the selective adsorption response of the modified electrode to 5-HT.
[0052] DPV of different concentrations of 5-HT was detected using the electrochemical sensor of this invention (0.1M Tris-HCl buffer at pH 8.0). Figure 5 The DPV detection graph shown shows that the oxidation potential of 5-HT is between 0.25V and 0.30V. As the concentration of 5-HT increases, the response current on the electrode also increases, with a detection limit of 0.03μM. The peak current shows a good linear relationship with the 5-HT concentration, as shown... Figure 6 As shown, the calibration curve consists of two linear segments (0.5 μM – 30 μM) and another linear segment (30 μM – 150 μM). The slope of the calibration curve differs at low and high analyte concentrations. At lower analyte concentrations, the slope of the first linear segment of the calibration curve is high due to the large number of active sites. However, at higher analyte concentrations, the slope of the second linear segment of the calibration curve decreases due to the reduction in active sites.
[0053] Five glassy carbon electrodes were taken, cleaned, and five clean glassy carbon electrodes were obtained. The Zn-MOF / MWCNTs composite material prepared in the example was drop-coated onto the first clean glassy carbon electrode, and dried to obtain the first working electrode;
[0054] The Zn-MOF / MWCNTs composite material prepared in the example was drop-coated onto the second clean glassy carbon electrode. After drying, the Zn-MOF / MWCNTs composite material prepared in the example was drop-coated again and dried to obtain the second working electrode.
[0055] The Zn-MOF / MWCNTs composite material prepared in the three examples was drop-coated onto the third clean glassy carbon electrode. After each drop-coating, the electrode was dried to obtain the third working electrode.
[0056] The Zn-MOF / MWCNTs composite material prepared in the previous example was drop-coated onto the fourth clean glassy carbon electrode. After each drop-coating, the electrode was dried to obtain the fourth working electrode.
[0057] The Zn-MOF / MWCNTs composite material prepared in the previous example was drop-coated five times onto the fifth clean glassy carbon electrode. After each drop-coating, the material was dried to obtain the fifth working electrode.
[0058] The five working electrodes were used as the working electrodes of the electrochemical sensor of this invention. Stability tests were performed on each electrode in a 0.1M Tris-HCl buffer solution containing 50 μM 5-HT at pH 8.0, with the same 5-HT concentration. This test assessed the I0 of the five working electrodes. pa ,have to Figure 7 The stability test graph is shown below. Figure 7As can be seen, the peak current detected by each modified electrode does not change significantly, with an RSD of 1.496%. This indicates that the electrochemical sensor based on NiZn-MOF / MWCNTs has good reproducibility.
[0059] After storing the five working electrodes that have undergone stability testing for 7 days, DPV tests were then performed on each of them. Figure 8 The peak current still maintains 99.8% of its initial value. This indicates that the electrochemical sensor based on NiZn-MOF / MWCNTs has good stability.
[0060] In a 10 mM 5-HT buffer solution, interfering agents UA, L-Cys, L-Arg, L-Phe, L-Gly, L-Tyr, L-Lys, AA, DA, and KCl were added. The concentration of each interfering agent in the buffer solution after addition was 100 mM. DPV testing was performed using the electrochemical sensor of this invention, and the peak current showed almost no change. Figure 9 The results show that the NiZn-MOF / MWCNTs electrochemical sensor prepared by the method of this invention has good anti-interference ability against 5-HT.
Claims
1. A nickel-based 5-HT electrochemical sensor using dithiones-transition metal MOFs / MWCNTs / GCE, comprising a working electrode, a reference electrode, a counter electrode, and a buffer solution, characterized in that, The working electrode is prepared as follows: 1) Based on the ratio of 4.5 mmol of P2S5, 1.5 mmol of NiCl2·6H2O, and 20 mL of dioxane required for 3 mmol of dimethyl 4,4'-(2-hydroxyacetyl)benzoate, take dimethyl 4,4'-(2-hydroxyacetyl)benzoate, P2S5, dioxane, and NiCl2·6H2O respectively. Reflux 4,4'-(2-hydroxyacetyl)benzoate and P2S5 in dioxane at 90 °C for 12 h, cool to room temperature, filter, and obtain the filtrate; NiCl2·6H2O was dissolved in distilled water at a ratio of 1.5 mmol of NiCl2·6H2O to 5 ml of distilled water to obtain a NiCl2 solution. Add the NiCl2 solution to the filtrate, reflux at 82 °C for 2 hours, concentrate, cool in an ice-water bath, filter and collect the residue, wash with dioxane, water, ethanol and diethyl ether respectively, and dry to obtain [Ni(C2S2(C6H4COOCH3)2)2]; 2) Based on the ratio of 30 mL tetrahydrofuran and 10 mmol KOH required for 1 mmol of [Ni(C2S2(C6H4COOCH3)2)2], take [Ni(C2S2(C6H4COOCH3)2)2], tetrahydrofuran and KOH respectively; Dissolve KOH in water at a ratio of 10 mmol of KOH to 10 mL of water to obtain a KOH solution. [Ni(C2S2(C6H4COOCH3)2)2] was dissolved in tetrahydrofuran, and then KOH solution was added. The mixture was stirred and refluxed at 60 °C for 10 hours, cooled to room temperature, and concentrated. The resulting product was completely dissolved in water, filtered, and the pH of the filtrate was adjusted to 6 with 1 M HCl to obtain a solid. The solid was washed with water and dried to obtain [Ni(C2S2(C6H4COOH)2)2]. 3) Take water and anhydrous ethanol in a volume ratio of 1:1, and dissolve the anhydrous ethanol in water to obtain the first solvent; N,N-dimethylformamide and anhydrous ethanol were taken in a volume ratio of 3:
1. N,N-dimethylformamide was dissolved in anhydrous ethanol to obtain a second solvent. According to the ratio of 0.014 mmol of [Ni(C2S2(C6H4COOH)2)2], 5.08 mL of the first solvent, and 0.52 mL of the second solvent required for 0.096 mmol of Zn(NO3)2·4H2O, Zn(NO3)2·4H2O, [Ni(C2S2(C6H4COOH)2)2], the first solvent, and the second solvent were prepared respectively. Zn(NO3)2·4H2O was dissolved in the first solvent to obtain the first solution, and [Ni(C2S2(C6H4COOH)2)2] was dissolved in the second solvent to obtain the second solution. The first solution was added to the second solution, and the mixture was ultrasonically mixed. The mixture was kept at 80°C for 24 hours, cooled to room temperature, filtered, and the product was washed with ethanol to obtain NiZn-MOF. 4) According to the ratio of 30 mg of carboxylated carbon nanotubes and 10 mg of Ni Zn-MOF added to 10 mL of N,N-dimethylformamide, carboxylated carbon nanotubes and Ni Zn-MOF respectively, the carboxylated carbon nanotubes and Ni Zn-MOF were added to DMF, ultrasonically dispersed for 2 h, and dried to obtain Ni Zn-MOF / MWCNTs; 5) Disperse Ni Zn-MOF / MWCNTs in DMF, sonicate to homogenize, and obtain a dispersion. Drop the dispersion onto the treated glassy carbon electrode and dry it under infrared light to obtain the working electrode.
2. The nickel-based dithioene-transition metal MOFs / MWCNTs / GCE 5-HT electrochemical sensor as described in claim 1, characterized in that: Preparation of carboxylated carbon nanotubes: HNO3 with a volume ratio of 1:3 and H2SO4 with a volume molar concentration of 4.0 mol / L were mixed to form an acid solution. Carbon nanotubes were added to the acid solution at a ratio of 100 mg of carbon nanotubes to 20 mL of acid solution. The solution was then vigorously magnetically stirred at room temperature for 18 h to obtain carboxylated carbon nanotubes.
3. The nickel-based dithioene-transition metal MOFs / MWCNTs / GCE 5-HT electrochemical sensor as described in claim 1, characterized in that: In step 5), the treated glassy carbon electrode is prepared as follows: the glassy carbon electrode is polished with Al2O3 powder, ultrasonically washed with ethanol and ultrapure water respectively, and dried under an infrared lamp to obtain the treated glassy carbon electrode.