CN114561020A

CN114561020A - Metal organic framework-Cu nano material for electrochemical sensor and preparation method and application thereof

Info

Publication number: CN114561020A
Application number: CN202210185333.0A
Authority: CN
Inventors: 梁莹; 黄琳琰; 李晨烨; 林佳妮; 蔡鑫如; 徐一新
Original assignee: Shanghai University of Medicine and Health Sciences
Current assignee: Shanghai University of Medicine and Health Sciences
Priority date: 2022-02-28
Filing date: 2022-02-28
Publication date: 2022-05-31
Anticipated expiration: 2042-02-28
Also published as: CN114561020B

Abstract

The invention relates to a metal organic framework-Cu nano material for an electrochemical sensor, a preparation method and application thereof, wherein the material is prepared by the following steps: (1) dissolving a copper source in deionized water, adding phosphoric acid, reacting, centrifuging, washing and drying to obtain CHP; (2) dispersing CHP in deionized water, adding a DMF (dimethyl formamide) solution of trimesic acid, reacting, centrifuging, washing and drying to obtain CHP @ Cu₃(BTC)₂A material; (3) taking CHP @ Cu₃(BTC)₂Dispersing the materials in anhydrous ether, adding DMTZ, reacting, centrifuging, washing and drying to obtain the target product. The material has the advantages of large specific surface area, rich pore channel structure, strong electrical conductivity, and capability of enhancing lead adsorption and accelerating electron transfer, and greatly reducing detectionAnd (6) measuring the limit. Compared with the prior art, the material compounded by the metal organic framework-Cu nano material and the glassy carbon electrode has the advantages of higher sensitivity, stronger anti-interference performance, better detection reproducibility and stability, small and simple required equipment and quick detection.

Description

Metal organic framework-Cu nano material for electrochemical sensor and preparation method and application thereof

Technical Field

The invention belongs to the technical field of electrochemical sensors, and relates to a metal organic framework-Cu nano material for an electrochemical sensor, and a preparation method and application thereof.

Background

Lead is an accumulative heavy metal, and once discharged into the environment, the lead can cause serious pollution to air, land, water sources and the like, and even lead can cause serious damage to various systems of human bodies, such as nerves, digestion, kidneys and the like after being circularly enriched by a food chain. It is worth noting that, in the early stage of accumulation, the concentration of lead in human body is low, no obvious clinical symptoms exist, if the lead cannot be treated in time, the consequences are very serious, and the hiding property of Pb is one of the factors causing harm. Therefore, establishing a method for quickly, sensitively and quantitatively detecting lead is an excellent strategy for preventing lead poisoning.

Common methods for detecting Pb include atomic absorption spectrometry, inductively coupled plasma method, high performance liquid chromatography and the like, but the methods have the disadvantages of complex sample pretreatment, huge experimental equipment, high price, long operation time and the like. In addition, the detection method for Pb in the prior art is low in sensitivity, easy to be interfered by other substances, and poor in detection reproducibility and stability.

At present, no electrochemical sensor based on a metal organic framework-Cu nano material can be applied to quantitative analysis of heavy metal lead ions to realize high-sensitivity rapid detection of the lead ions.

Disclosure of Invention

The invention aims to provide a metal organic framework-Cu nano material for an electrochemical sensor and a preparation method and application thereof, so as to overcome the defects that the Pb detection method in the prior art is low in sensitivity, easy to be interfered by other substances, poor in detection repeatability and stability, large in required experimental equipment, complex in sample pretreatment, high in cost, long in operation time and the like.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a preparation method of a metal organic framework-Cu nanometer material for an electrochemical sensor, which comprises the following steps:

(1) dissolving a copper source in deionized water, adding phosphoric acid, reacting, centrifuging, washing and drying to obtain CHP;

(2) dispersing the obtained CHP in deionized water, adding N, N-Dimethylformamide (DMF) solution of trimesic acid, reacting, centrifuging, washing, and drying to obtain CHP @ Cu₃(BTC)₂A material;

(3) taking the obtained CHP @ Cu₃(BTC)₂The material is dispersed in anhydrous ether, then 2, 5-Dimercaptothiadiazole (DMTZ) is added, and a target product is obtained through reaction, centrifugation, washing and drying.

Further, in the step (1), the copper source is copper acetate.

Further, in the step (1), the ratio of the addition amounts of the copper source, the deionized water and the phosphoric acid is (2-4) g: 80mL of: (0.4-0.6) mL, optionally 3.2 g: 80mL of: 0.544 mL.

Further, in the step (1), the reaction temperature is 120-.

Further, in the step (1), a solid is obtained by centrifugation, and then the obtained solid is washed 3 times with deionized water and ethanol and then dried for 12 hours at 25 ℃.

Further, in the step (2), the concentration of the N, N-dimethylformamide solution of trimesic acid is 0.025 mol. L^-1。

Furthermore, the addition ratio of the CHP, the deionized water and the N, N-dimethylformamide solution of the trimesic acid is (1-2) g: 51mL of: (40-50) mL, optionally 1.3 g: 51mL of: 45 mL.

Further, in the step (2), before the reaction, the pH of the mixed solution obtained after adding the N, N-dimethylformamide solution of trimesic acid was adjusted to 6.

Further, in the step (2), the reaction temperature is 20-40 ℃, optionally 25 ℃, and the reaction time is 1-3 hours, optionally 1 hour.

Further, in the step (2), a solid is obtained by centrifugation, and then the obtained solid is washed 3 times with ethanol.

Further, in the step (2), the drying temperature is 40 ℃, and the drying time is 12 h.

Further, in the step (3), CHP @ Cu₃(BTC)₂The ratio of the addition amounts of the material, dehydrated ether and DMTZ is (0.1-0.3) g:20mL (50-150) mg, optionally 0.2g:20mL:50mg, 0.2g:20mL:100mg or 0.2g:20mL:150 mg.

Further, in the step (3), the reaction temperature is 20-40 ℃, optionally 25 ℃, and the reaction time is 12-36 hours, optionally 24 hours.

Further, in step (3), a solid was obtained by centrifugation, and then the obtained solid was washed 3 times with water and ethanol, respectively.

Further, in the step (3), the drying temperature is 60 ℃ and the drying time is 12 h.

The second technical scheme of the invention provides a metal organic framework-Cu nano material for an electrochemical sensor, wherein the metal organic framework-Cu nano material is rod-shaped, and the average length is 10 mu m.

The third technical scheme of the invention provides an application of the metal organic framework-Cu nano material, the metal organic framework-Cu nano material is used for detecting heavy metal ions, and the detection process comprises the following steps:

s1: dispersing the metal organic framework-Cu nano material in a solvent to obtain a mixed solution;

s2: dripping the obtained mixed solution on a glassy carbon electrode, and drying to obtain a modified electrode;

s3: and taking the obtained modified electrode as a working electrode, taking a calomel electrode as a reference electrode, taking a platinum wire electrode as a counter electrode, respectively taking acetic acid-sodium acetate buffer solutions containing heavy metal ions with different concentrations as electrolytes for electrodeposition, then measuring the stripping peak current by adopting SWV, establishing a standard curve according to the stripping peak current and the corresponding concentration of the heavy metal ions to obtain a standard curve equation, measuring the stripping peak current of the sample to be detected under the same condition, and then calculating the content of the heavy metal ions in the sample to be detected according to the stripping peak current and the standard curve equation.

Further, the heavy metal ions are lead ions.

Further, in step S1, the solvent is a mixture of chitosan solution and ethanol.

Furthermore, the volume ratio of the chitosan solution to the ethanol is 1: 1.

further, the concentration of the chitosan solution is 1 mg/ml^-1。

Further, in step S1, the mass-to-volume ratio of the metal organic framework-Cu nanomaterial to the solvent is 5 mg: 200 μ L.

Further, in step S2, the dropping amount of the mixed solution is 0.57 to 1.13 μ L/mm²Preferably 0.71. mu.L/mm²。

Further, in step S2, the glassy carbon electrode is pre-treated before dispensing as follows:

(1) al for glassy carbon electrode₂O₃Grinding and polishing the powder on chamois leather to obtain smooth mirror surface, washing, drying and placing in H₂SO₄Soaking in the solution, scanning to be stable by using a cyclic voltammetry method, and washing to obtain an activated glassy carbon electrode;

(2) al for the activated glassy carbon electrode₂O₃And grinding and polishing the powder on chamois leather until the mirror surface is smooth, and then washing and airing to finish the pretreatment of the glassy carbon electrode.

Further, in step S3, during the electrodeposition process, the voltage is-1.3 to-0.8V, preferably-1V, and the deposition time is 130 to 330S, preferably 250S.

Further, in step S3, the pH of the acetic acid-sodium acetate buffer is 4 to 6, preferably 5.0.

Further, in step S3, after the electrodeposition is completed, the mixture is left to stand for 10 seconds and then eluted.

Further, in step S3, during the dissolution peak current test, the potential sweep range is-1.0V to 0V.

Further, in step S3, the concentration of heavy metal ions in the acetic acid-sodium acetate buffer solution is 0.01, 0.03, 0.05, 0.08, 0.1, 0.2, 0.4, 0.8, 3, 7, 10, 20, 30, 50, or 80nmol · L^-1。

The metal organic framework-Cu nano material can be used for detecting heavy metal ions, the adopted detection method is an electrochemical analysis method, namely stripping voltammetry (SWV), the method has the advantages of small and simple required equipment, high sensitivity, high detection speed, easy analysis of experimental results and the like, and has great development space in the field of real-time on-site detection. The stripping voltammetry is to electrolyze for a certain time under the potential of limiting current generated by polarographic analysis of a substance to be detected, then change the potential of an electrode to re-strip the substance enriched on the electrode, and perform quantitative analysis according to a voltammetry curve obtained in the stripping process. The method has the characteristics of high sensitivity, rapid detection and capability of detecting various ions.

Metal Organic Frameworks (MOFs) are a class of crystalline porous materials of network structure connected by the interaction of inorganic metal centers with organic ligands. Due to the advantages of abundant metal active sites, strong adsorption capacity, strong adjustable chemical property and good thermal stability, and the advantages of magnetism, optics, catalysis and stability of the functional micro/nano particle (MP/NP) inner core, the functional micro/nano particle metal organic framework (MP/NP @ MOF) has huge application potential in the aspects of adsorption, gas storage, catalysis, chemical sensing and the like. Especially, the construction of the core/shell structure of the controllable function MP/NP @ MOF not only avoids the polymerization of the core and keeps the characteristics of the core, but also obtains the synergistic effect by integrating the functions of the MOF shell and the MP/NP core, and greatly improves the application potential. Copper trimesate (Cu)₃(BTC)₂) The copper-based mesoporous material is a three-dimensional structure consisting of metal central copper and a ligand trimesic acid, has the characteristics of high specific surface area, high pore volume and controllable morphology, and is very representative in metal organic framework materials.

The invention adopts an in-situ template method and utilizes an active shell of hydroxyl copper phosphate (CHP) asThe source of metal ions is converted to well-defined Cu in situ on the CHP core at room temperature₃(BTC)₂The method effectively avoids the self-nucleation of the MOF in the solution, successfully assembles crystal unit MP @ MOF with clear limit, and uses DMTZ functionalized MP @ MOF to obtain the MOFs composite material (DMP-Cu). Because the properties of the relatively stable core are retained during synthesis, the stability and adsorption properties of the resulting material are greatly improved.

The chitosan molecule is composed of acetamido, hydroxyl and amino, so that the chitosan has special adsorption and flocculation capacity. In the wastewater treatment, chitosan is usually utilized to achieve the effect of efficiently trapping heavy metal ions by virtue of the flocculation effect, and in addition, chitosan can perform coordination reaction with metal ions and can better fit with materials, so that the chitosan is used as an adhesive to modify a GCE electrode, so that the materials are not easy to fall off in the detection process, and the stability of the electrochemical detection of the heavy metals is improved. In addition, the chitosan has affinity to cells and is biodegradable, and the possibility of environmental pollution does not exist in the using process.

Compared with the prior art, the invention has the following advantages:

(1) the method adopts an in-situ template method, utilizes an active shell of hydroxyl copper phosphate (CHP) as a source of metal ions, and converts the active shell into Cu with clear boundary in situ on a CHP inner core₃(BTC)₂The method effectively avoids the self-nucleation of MOF in the solution, successfully assembles crystal unit MP @ MOF with clear limit, and uses DMTZ functionalized MP @ MOF to obtain the MOFs composite material, and the finally obtained metal organic framework-Cu nanometer material has good stability and adsorbability due to the property of relatively stable inner core reserved in the synthesis process;

(2) the modified electrode obtained by compounding the metal organic framework-Cu nano material and the glassy carbon electrode can be used as an electrochemical sensor for detecting lead ions, and the modified electrode is used for detecting Pb in a water sample²⁺The material has specific adsorption capacity, and has strong anti-interference performance, reproducibility and stability;

(3) the metal organic framework-Cu nano material has larger specific surface areaThe porous structure is rich, can strengthen lead adsorption and accelerate electron transfer, has stronger electrical conductivity, and can greatly reduce the detection limit of heavy metal lead, the detection limit is as low as 0.003 nmol.L^-1(S: N is 3:1), the sensitivity is high;

(4) the invention is based on metal organic framework-Cu nano material, and adopts SWV to lead²⁺Realizes high-efficiency and quantitative detection, and lead concentration is 1 multiplied by 10^-11～8×10^-8mol·L^-1Within the range of (1), the size of the stripping peak current and the concentration of lead ions show good linear relation, the required equipment is small and exquisite, simple and convenient, the detection is rapid, the experimental result is easy to analyze, complex sample pretreatment is not needed, the cost is lower, and the method has good linear relation to the Pb ion concentration²⁺The rapid real-time detection has certain application value.

Drawings

FIG. 1 shows a standard card of CHP and CHP, CHP @ Cu₃(BTC)₂An XRD spectrum of DMP-Cu-50;

fig. 2 is a Scanning Electron Microscope (SEM) image of each material: (A) CHP; (B) CHP @ Cu₃(BTC)₂；(C)DMP-Cu-50；(D)DMP-Cu-100；(E)DMP-Cu-150；

FIG. 3 is a scanning electron microscope-X-ray energy spectrum of each material: (A) CHP (CHP); (B) CHP @ Cu₃(BTC)₂；(C)DMP-Cu-50；

FIG. 4 is a cyclic voltammogram: (A) CHP/GCE, CHP @ Cu₃(BTC)₂The ratio of the concentration of the mixture to the concentration of the mixture is 5 mmol.L^- ¹K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L of^-1Cyclic voltammograms in KCl solution of (a); (B) DMP-Cu-50/GCE, DMP-Cu-100/GCE, DMP-Cu-150/GCE in 5 mmol.L^-1K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L of^-1Cyclic voltammogram in KCl solution;

FIG. 5 shows that the ratio of GCE, DMP-Cu-50/GCE, DMP-Cu-100/GCE, DMP-Cu-150/GCE is 2.5 μm.L^-1SWV pattern in lead solution;

FIG. 6 shows DMP-Cu-50/GCE at 5 mmol.L^-1K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L of^-1KCl ofSweeping speed cyclic voltammograms in solution;

FIG. 7 is a schematic view of: (A) DMP-Cu-50/GCE at different enrichment times for 2.5. mu. mol. L^-1Pb of²⁺SWV map of (1); (B) graph of enrichment time versus SWV peak current;

FIG. 8: (A) DMP-Cu-50/GCE at different enrichment potential pairs 2.5. mu. mol. L^-1Pb of²⁺SWV map of (1); (B) a plot of the enrichment potential versus SWV peak current;

FIG. 9: (A) DMP-Cu-50/GCE pairs prepared from different drop-applied amounts of DMP-Cu-50 solutions 2.5. mu. mol. L^-1Pb of²⁺SWV profile of the solution; (B) a relation graph of DMP-Cu-50 droplet coating quantity and SWV peak current;

FIG. 10: (A) DMP-Cu-50/GCE for 2.5. mu. mol. L in acetic acid-sodium acetate buffer solutions of different pH values^-1Pb of²⁺SWV map of (1); (B) a graph of the pH of the acetic acid-sodium acetate buffer solution versus the SWV peak current;

FIG. 11: (A) DMP-Cu-50/GCE at Pb²⁺The concentration is 0.01 nmol.L^-1～0.4nmol·L^-1A current response stripping voltammetry (SWV) profile of (a); (B) DMP-Cu-50/GCE at Pb²⁺The concentration is 0.8 nmol.L^-1～80nmol·L^-1A current response stripping voltammetry (SWV) profile of (a); (C) at low concentration of Pb²⁺In the range (0.01 nmol. L)^-1～0.4nmol·L^-1)Pb²⁺A standard curve of concentration versus current; (D) at high concentration of Pb²⁺In the range (0.8 nmol. L)^-1～80nmol·L^-1)Pb²⁺Standard curve of concentration versus current.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the materials or processing techniques are those conventionally used in the art.

In the following examples, 5 mmol. multidot.L was used^-1K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L^-1The KCl solution is prepared, wherein K is₃[Fe(CN)₆]And K₄[Fe(CN)₆]Purchased from Shanghai Tantake technologies, Inc. in a molar ratio of 1: 1.

example 1:

synthesis of CHP:

3.2g of copper acetate was added to 80mL of water, and the mixture was stirred uniformly, 0.544mL of phosphoric acid was slowly added dropwise, and the mixture was stirred for 1 hour. Adding the suspension into a reaction kettle after the suspension is uniformly mixed, putting the reaction kettle into an oven, and heating the reaction kettle for 4 hours at 140 ℃ under normal pressure. And after the reaction is finished, centrifuging to obtain a precipitate, washing for 3 times by using deionized water and ethanol respectively, and drying at room temperature for 12 hours to obtain a green solid, namely CHP.

Example 2:

CHP@Cu₃(BTC)₂synthesis of materials:

1.3g of CHP prepared in example 1 was added to 51mL of water, followed by stirring, and 45mL of a N, N-Dimethylformamide (DMF) solution of trimesic acid (0.025 mol. L)^-1) Adjusting the pH of the obtained mixed solution to 6 by using a 4% NaOH solution, stirring for 1h at 25 ℃, centrifugally recovering precipitate, washing for 3 times by using ethanol, and drying for 12h at 40 ℃ to obtain a product CHP @ Cu₃(BTC)₂A material.

Example 3:

synthesis of DMP-Cu material:

0.2g of CHP @ Cu prepared as described in example 2 was taken₃(BTC)₂The material was placed in a 50mL round bottom flask, 20mL of anhydrous ether was added, followed by the addition of DMTZ (A: 50 mg; B:100 mg; C: 150mg) of different masses, respectively. Stirring for 24h at 25 ℃, centrifuging to obtain a solid, washing with water and ethanol for 3 times respectively, and drying in a vacuum oven at 60 ℃ for 12h to obtain DMP-Cu materials (named as DMP-Cu-50, DMP-Cu-100 and DMP-Cu-150 respectively, wherein the DMP-Cu-50 is a DMP-Cu material prepared by adding 50mg of DMTZ, and the like) with different proportions.

For the CHP obtained in example 1 and the CHP @ Cu obtained in example 2₃(BTC)₂Materials, DMP-Cu materials from example 3And (3) characterization:

to determine the phase of the DMP-Cu material produced, analytical characterization was performed using X-ray diffraction (XRD) at 2 θ angles in the range of 10 to 50. As shown in FIG. 1, the diffraction peak of the synthesized template CHP was compared with that of the standard card [ Cu ]₂(OH)PO₄，JCPDS:No.36-0404]And comparing, wherein the peak heights, peak shapes and peak-out angles of the two are basically consistent, and the characteristic diffraction peaks are basically superposed. In situ conversion to Cu₃(BTC)₂After the shell crystallization, new diffraction peaks appeared in the crystals (as indicated by the arrows in fig. 1). The main peak of the DMP-Cu material (DMP-Cu-50) obtained after DMTZ functionalization is consistent with the main peak before modification, because a stable template core of CHP exists, the diffraction peak of CHP can still be observed in a DMP-Cu-50 map, and the structure of MOF is kept good.

The morphological structure of the material was characterized and analyzed by Scanning Electron Microscopy (SEM). A, B, C, D, E in FIG. 2 are CHP, CHP @ Cu, respectively₃(BTC)₂And the material characterization diagrams of the DMP-Cu-50, DMP-Cu-100 and DMP-Cu-150 materials under a scanning electron microscope. As shown in fig. 2(a), the crystals of CHP have a typical columnar structure, which is represented by small and densely aggregated nanorods, and the shell is rough. CHP @ Cu₃(BTC)₂Are prepared by in situ conversion of a CHP template shell into a well-defined MOF crystal shell. When a solution of trimesic acid in N, N-Dimethylformamide (DMF) was added to the aqueous solution in which the CHP template was dispersed at room temperature, the solution changed color from green to light blue, indicating Cu₃(BTC)₂Is generated. As shown in fig. 2(B), the CHP template shell is converted in situ into a well-defined crystalline shell. As shown in fig. 2(C), (D), and (E), the DMTZ-modified composite material can be observed that the DMP-Cu material obtained by using DMTZ functionalization has a similar size, but a rougher surface, and the surface morphology of the newly generated material is flower-shaped, so that the specific surface area can be greatly increased, the pore structure is enriched, the effects of enhancing adsorption and accelerating electron transfer can be achieved in the lead enrichment process, the electrical conductivity is enhanced, and the detection limit of heavy metal lead can be greatly reduced. As can be seen, during the synthesis process of the DMP-Cu material, the relatively stable core structure is kept, so that the stability and the effective adsorption of the material are realizedThe performance is greatly improved.

To further confirm Cu₃(BTC)₂And successful assembly of DMTZ to CHP surfaces, the DMP-Cu material was analyzed by SEM-EDS for elemental weight distribution and atomic content. As shown in fig. 3 and table 1, the atomic content of Cu gradually decreased with the two-step functionalization of CHP, consistent with the expected results. Meanwhile, in DMP-Cu-50, the presence of S element was detected. DMTZ again demonstrated successful functionalization.

TABLE 1 CHP, CHP @ Cu₃(BTC)₂SEM-EDS analysis data summary table of DMP-Cu-50 material

Example 4:

a glassy carbon electrode (GCE, diameter 3mm) was successively treated with Al having particle diameters of 0.3 μm and 0.05 μm₂O₃Polishing the powder on a chamois leather to a mirror surface, washing with water, sequentially carrying out ultrasonic cleaning in absolute ethyl alcohol and water for 1min respectively, and airing to obtain clean GCE. Clean GCE is placed in 1 mol.L^-1H of (A) to (B)₂SO₄Soaking in the solution for 5min, and performing cyclic voltammetry at 0.05 V.s^-1Scanning at a scanning speed of-0.2-2.0V until the scanning speed is stable, taking out the electrode, and respectively carrying out ultrasonic cleaning for 1min in ethanol and water to obtain the activated glassy carbon electrode (A-GCE). A-GCE was treated with 0.3 μm and 0.05 μm Al₂O₃Grinding and polishing the powder on chamois leather until the mirror surface is smooth, washing the powder by using secondary distilled water, and drying the powder for later use. 5mg of DMP-Cu-50, DMP-Cu-100 and DMP-Cu-150 prepared in example 3 were placed in different centrifuge tubes, and 100. mu.L of ethanol and 100. mu.L of chitosan solution (1 mg. ml) were added^-11mg of chitosan is dissolved in 1ml of 10 wt% acetic acid solution), and the mixture is evenly mixed by ultrasonic to obtain DMP-Cu-50 solution, DMP-Cu-100 solution and DMP-Cu-150 solution with the concentration of 0.025 mg/microliter, and 5 microliter of the obtained solution is respectively dripped and coated on the center of the glassy carbon electrode after treatment (the dripping area is 7.065 mm)²The dropping amount is 0.71 mu L/mm²) Drying and cooling to obtain three MOF material modifiedGCE, named DMP-Cu-50/GCE, DMP-Cu-100/GCE, DMP-Cu-150/GCE. Preparation of CHP, CHP @ Cu as above₃(BTC)₂The GCE modified by the material is respectively named as CHP/GCE and CHP @ Cu₃(BTC)₂/GCE。

Example 5:

the performance of the modified electrode prepared in example 4 was characterized:

by studying the different electrodes at 5 mmol. L^-1K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L of^-1In KCl solution of (A)²⁺/Fe³⁺The difference between the current and the potential of the oxidation-reduction peak of the electricity pair can judge the electrochemical performance of the material. FIG. 4(A) shows CHP/GCE, CHP @ Cu₃(BTC)₂CV scans of/GCE, and DMP-Cu-50/GCE. It can be seen that with further functionalization of the MOF material, Fe²⁺/Fe³⁺The oxidation-reduction peak current of the electric couple on the DMP-Cu material is larger, and the oxidation-reduction peak potential difference (delta Ep) is also smaller, which shows that the DMP-Cu-50/GCE electrode has stronger catalytic action on the oxidation-reduction reaction and better reversibility of the oxidation-reduction reaction on the surface of the electrode.

In order to investigate the effect of DMTZ with different addition amounts on the modified electrode during the synthesis of DMP-Cu, CV scans of DMP-Cu-50/GCE, DMP-Cu-100/GCE, and DMP-Cu-150/GCE were compared as shown in FIG. 4 (B). The results show that Fe²⁺/Fe³⁺The redox peak current of the electrode pair on the DMP-Cu-50/GCE electrode is the largest, and is consistent with the characterization results of XRD and SEM. Therefore, DMP-Cu-50/GCE can be selected as the optimal modified electrode for Pb²⁺Detection of (3).

FIG. 5(A) shows a lead solution (2.5 μm. L) of bare GCE and DMP-Cu-50/GCE, DMP-Cu-100/GCE, DMP-Cu-150/GCE obtained in example 4^-1) The comparison of SWV curves in (1) shows that the composite electrode of DMP-Cu and GCE is used for detecting Pb from FIG. 5²⁺Although the elution sites of (a) are shifted, the peak current for elution is significantly higher than that of the bare GCE. The reason is that during the synthesis process, DMF and water form shell layer crystals with clear structures on the surface of the CHP template, so that the self-nucleation of MOF in solution can be effectively avoided, and most of nanorod cores of the CHP template are still coveredThe specific surface area is increased after the retention and modification by DMTZ, thereby enhancing the conductivity and the electron transfer, leading the heavy metal ion lead to be easier to be absorbed and enriched, and improving the determination of Pb²⁺The sensitivity of (2). The maximum peak current of DMP-Cu-50/GCE was observed at 5 mmol.L by CV method^-1K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L of^-1The results of the scans of the KCl solution are consistent, so that DMP-Cu-50/GCE can be used as an electrochemical sensor for Pb²⁺High sensitivity detection of the solution.

Example 6:

influence of the scanning rate:

the reaction mechanism of the modified electrode surface prepared in example 4 was presumed by studying the influence of the scanning rate on the electrochemical response. FIG. 6 shows DMP-Cu-50/GCE at 5 mmol.L^-1K₃[Fe(CN)₆]/K₄[Fe(CN)₆]0.1 mol. L^-1Cyclic voltammograms of the KCl solution scanned at different sweep rates. When the sweeping speed is from 60mV s^-1～180mV·s^-1The redox peak current response increased with increasing magnitude, but the redox potential difference (Δ Ep) also increased progressively, indicating that too fast a scan rate may deteriorate the reversibility of the redox reaction occurring at the electrode surface. On the other hand, it was found by calculation (see the inset in fig. 5B) that the reduction peak current (Ipa) and the sweep rate (ν) are linearly related, and the linear regression equation was 0.02948 ν + 19.00. This indicates that the process is an electrochemical process controlled by adsorption on DMP-Cu-50/GCE. As the scan rate decreases, the current response decreases and the sensitivity deteriorates. On the other hand, as the scanning rate increases, the current response also increases, and the sensitivity increases, but the reversibility of the redox reaction becomes poor, and the optimum scanning rate is 100mV · s^-1。

Example 7:

enrichment time for Pb²⁺Influence of dissolution peak current:

this example uses DMP-Cu-50/GCE prepared in example 4 as the experimental subject to investigate the enrichment time for Pb²⁺Influence of dissolution peak current. The enrichment time influences the detection limit and sensitivity of heavy metalsIs one of the important factors. Since the modified electrode firstly needs to be stirred at Pb²⁺Enrichment in solution, so that the prolongation of the enrichment time is beneficial to the Pb on the surface of the electrode²⁺Adsorption of (3). FIG. 7(A) shows DMP-Cu-50/GCE at different enrichment times for 2.5. mu. mol. L^-1Pb of²⁺The analysis result of the SWV graph of (A) in FIG. 7(B) shows that the peak current has a dependency on the enrichment time of the metal ion lead, and the elution peak current increases as the enrichment time increases from 130s to 250 s. However, as the enrichment time is prolonged, the peak current of dissolution is reduced. Shows that in the initial stage of adsorption, the adsorption time is increased to be beneficial to Pb²⁺The enrichment on the surface of the electrode, but when the concentration of metal ions on the surface of the electrode is saturated, the metal active sites can not continuously adsorb Pb any more²⁺While the stirring is carried out, Pb adsorbed on the surface of the material²⁺Easily fall off, thereby influencing the detection limit, and the optimal enrichment time is 250 s.

Example 8:

pair of deposition potential Pb²⁺Influence of dissolution peak current:

this example investigated the deposition potential versus Pb using the DMP-Cu-50/GCE prepared in example 4 as the experimental subject²⁺Influence of dissolution peak current. In the elution analysis of heavy metal ions, the choice of the deposition potential is important to obtain the best sensitivity. Therefore, the effect of the deposition potential on the dissolution peak current after 250s enrichment was investigated in 0.1M acetic acid-sodium acetate buffer, pH 5.0. FIG. 8(A) shows DMP-Cu-50/GCE at different enrichment potentials for 2.5. mu. mol. L^-1Pb of²⁺The analysis result of the SWV of (1) is shown in FIG. 8(B), and Pb is present when the deposition potential is decreased from-0.8V to-1.0V²⁺Gradually increases the peak current. This is because the oxidation reaction is more difficult to occur and the reduction reaction is more likely to occur with the negative shift of the deposition potential, so that the reduction peak current becomes larger. However, Pb was observed when the deposition potential continued to decrease to less than-1.0V²⁺The response of (c) decreases. This is because hydrogen evolution reaction occurs on the surface of the electrode, and hydrogen bubbles generated during the reaction adhere to the surface of the electrode, blocking Pb²⁺The further adsorption of the solution reduces the peak current after dissolution, and simultaneously can avoid real samplesCo-deposition of other metal ions in the analysis. Therefore, the optimum deposition potential is-1.0V.

Example 9:

amount of dropping to Pb²⁺Influence of dissolution peak current:

the GCE modified by the MOF material in example 4 is prepared by dripping the DMP-Cu material on the GCE electrode, so that the dripping amount of the DMP-Cu material determines the number of metal active sites on the surface of the electrode, and the electrochemical detection of lead is greatly influenced. In this example, the DMP-Cu-50 solution (0.025 mg. mu.L) prepared in example 4 was used^-1)4 muL, 5 muL, 6 muL, 7 muL and 8 muL are dripped on the surface of a GCE electrode to prepare a modified electrode material (the dripping areas are 7.065mm²The corresponding dispensing amounts are 0.57, 0.71, 0.85, 0.99 and 1.13 muL/mm respectively²) And then performing electrochemical detection. FIG. 9(A) shows the different drop amounts of DMP-Cu-50 solution versus 2.5. mu. mol. L^-1Pb of²⁺The SWV of the solution was analyzed and the peak current was maximized when the volume of the solution applied was 5. mu.L, as shown in FIG. 9 (B). The dripping amount is too small, so that the GCE central mirror surface cannot be covered, the number of metal active sites is small, and the electrochemical response is poor; and the dripping amount is too large, the surface of the electrode is covered with the modifying material too thickly, but the electron transfer is blocked, the conductivity is reduced, and the response is weakened. In addition, when stirring and enriching, the dropping amount is too much, which easily causes the dropping material to be lumpy and fall off, so that the detection effect is deteriorated, therefore, 0.71 mu L/mm²Is the most suitable for dripping.

Example 10:

pH value of buffer to Pb²⁺Influence of dissolution peak current:

in this example, the pH of the buffer was investigated for Pb using DMP-Cu-50/GCE prepared in example 4 as the test object²⁺Influence of dissolution peak current. The pH value of the buffer solution has a great influence on the peak current, so that the proper pH value is selected to be Pb²⁺The determination of (2) is of great importance. FIG. 10(A) shows DMP-Cu-50/GCE in 0.1M acetic acid-sodium acetate buffer solutions of different pH vs 2.5X 10^- ⁶mol·L^-1The SWV response curve of the lead solution of (1) and the analysis result are shown in FIG. 10(B), and it is understood that as the pH value is increased from 4.0 to 5.0,Pb²⁺the peak current of (a) increases and reaches a maximum at a pH of 5.0, and the dissolution current decreases as the pH continues to increase. This is because too high pH easily causes hydrolysis reaction of lead ions, and pH5.0 is the optimum pH of the buffer solution.

Example 11:

reproducibility, stability and interference immunity of DMP-Cu-50/GCE prepared in example 4:

the reproducibility and stability of the electrochemical sensor are important criteria for judging the detection capability. The DMP-Cu-50/GCE prepared in example 4 was placed at 2.5. mu.m.L^-1The measurement was repeated 10 times, and the relative standard deviation of the dissolution peak current was 3.25%. Then, the DMP-Cu-50/GCE prepared by the same method was measured under the same experimental conditions for a plurality of times with a relative error of 4.03% (n ═ 10). In addition, the modified electrode had only 8.2% peak current loss after 10 days of storage. The DMP-Cu-50/GCE is proved to have good reproducibility and stability and good detection capability when used as an electrochemical sensor.

In actual sample analysis, interference of unknown substances is inevitable, so that modifying the anti-interference performance of the electrode is one of important detection standards. At a lead ion concentration of 2.5 μm.L^-1The solution of (A) is simultaneously added with Na⁺，Cl^-，Mg²⁺，SO₄ ^2-，Fe²⁺，CO₃ ^2-，K⁺，PO₄ ^2-，Hg²⁺，Cr³⁺With urea, glucose, aniline, vitamin C, DMP-Cu-50/GCE was evaluated for Pb²⁺The amounts and concentrations of the competitive ions, urea, glucose, aniline and vitamin C are the same. Experimental results show that the interference of each ion to SWV peak current is small and is less than 5%, and the evidence that DMP-Cu-50/GCE has no influence on Pb in water sample²⁺The DMP-Cu-50/GCE has specific adsorption capacity, so that the DMP-Cu-50/GCE can be used as an electrochemical sensor to be more efficiently and sensitively applied to detection of lead ions in practical samples.

Example 12:

in examples 7 to 10, SWV was used to measure a lead solution of a certain concentration, to determine the position and size of the lead peak, to optimize the enrichment time (130 s-330 s), the deposition potential (-1.3V-0.8V), the drop coating amount (4. mu.l-8. mu.l), the pH of the acetic acid-sodium acetate buffer (4-6), and to determine the optimal enrichment time (250s), the optimal deposition potential (-1.0V), the optimal drop coating amount (5. mu.l) and the pH of the acetic acid-sodium acetate buffer (5.0).

Detection linearity and minimum detection limit of heavy metal lead:

firstly, a three-electrode system for electrochemical detection is established for measuring heavy metal lead. The reference electrode was calomel electrode, the counter electrode was platinum wire electrode, the working electrode was DMP-Cu-50/GCE prepared in example 4, and the three-electrode system was placed in the presence of Pb²⁺In acetic acid-sodium acetate buffer (pH 5, 0.1 mol. L)^-1) Stirring and depositing for 250s under the potential of-1V by adopting a current-time method, stopping stirring, standing for 10s, and then dissolving by using SWV, wherein the scanning range is-1.0V-0V, and the dissolution peak position and the current magnitude of the lead are obtained. Finally, the potential was adjusted to 0.1V, and the electrode surface was cleaned for 120 seconds to remove the lead remaining on the electrode surface for the next test. The whole experiment comprises a series of steps of enrichment, dissolution and washing, and the detection is repeated for a plurality of times. Finally, a standard curve is established according to the peak current of the dissolution curve and the concentration of the lead solution so as to quantitatively determine the lead. Pb²⁺The concentration gradient is 0.01 nmol.L from low to high^-1，0.03nmol·L^-1，0.05nmol·L^-1，0.08nmol·L^-1，0.1nmol·L^-1，0.2nmol·L^-1，0.4nmol·L^-1，0.8nmol·L^-1，3nmol·L^-1，7nmol·L^-1，10nmol·L^-1，20nmol·L^-1，30nmol·L^-1，50nmol·L^-1And 80 nmol. L^-1。

As shown in FIGS. 11(A) and 11(B), following Pb²⁺The analysis results are shown in fig. 11(C) and 11(D) as the concentration increases and the lead elution peak increases: pb²⁺At a concentration of 0.01 nmol.L^-1～0.4nmol·L^-1And 0.8 nmol.L^-1～80nmol·L^-1In the range of DMP-Cu-50/GCE at Pb²⁺Ipa and Pb in solution²⁺At a concentration of (c) ofA good linear relationship. At low concentration (0.01 nmol. L)^-1～0.4nmol·L^-1) When the linear regression equation is that Ipa (mu A) is 17.27c (nmol. L)^-1)+7.12(R²0.9779); at high concentration (0.8 nmol. L)^-1～80nmol·L^-1) When the linear regression equation is shown in the specification, Ipa (mu A) is 0.5219c (nmol. L)^-1)+17.34(R²0.9896). The detection limit is 0.003 nmol.L^-1(S:N＝3:1)。

According to the limit index of lead specified in national food safety standard-pollutant limit in food, the lead limit of the packaged drinking water is the lowest, namely 0.01 mg.L^-1I.e. 4.826X 10^-8mol·L^-1. The blood lead level in human body exceeds 100ug L^-1(4.826×10^-7mol·L^-1) The possibility of lead exceeding is high, and DMP-Cu-50/GCE has the practical application capability of detecting lead ions with ultra-low concentration, can reach the national food safety detection standard, and has huge application potential in the aspect of field real-time detection of heavy metals in the future.

Example 13:

actual determination of tap water sample and seaweed water sample:

in the embodiment, the DMP-Cu-50/GCE obtained in the embodiment 4 is used as an electrochemical sensor to detect water samples. Wherein, the tap water sample is taken from a medicine laboratory of Shanghai health medical college, the seaweed water sample is taken from Changjiang river of Chongming island to sea, and the content of lead is measured by using a standard-adding recovery method. Pb obtained in example 12 based on the magnitude of the elution peak current²⁺The concentration-current relation curve obtains the concentration of each group, the recovery rate range is 104.00% -123.67%, and the result shows that DMP-Cu-50/GCE can realize the rapid and quantitative determination of lead ions in the environment, and has a large development space in the aspect of real-time on-site detection.

Example 14:

most of them were the same as in example 1, except that in this example, the amount of copper acetate added was changed to 2 g.

Example 15:

most of them were the same as in example 1, except that the amount of copper acetate added was changed to 4g in this example.

Example 16:

most of the results were the same as those in example 1, except that the amount of phosphoric acid added was changed to 0.4mL in this example.

Example 17:

most of the results were the same as those in example 1, except that the amount of phosphoric acid added was changed to 0.6mL in this example.

Example 18:

compared with example 1, most of the results are the same, except that in this example, "heating at 140 ℃ under normal pressure for 4 hours" is changed to "heating at 120 ℃ under normal pressure for 4 hours".

Example 19:

compared with example 1, most of the results are the same, except that in this example, "heating at 140 ℃ under normal pressure for 4 hours" is changed to "heating at 160 ℃ under normal pressure for 4 hours".

Example 20:

compared with example 1, most of the parts are the same, except that in this example, "heating at 140 ℃ under normal pressure for 4 h" is changed to "heating at 140 ℃ under normal pressure for 2 h".

Example 21:

compared with example 1, most of the results are the same, except that in this example, "heating at 140 ℃ under normal pressure for 4 h" is changed to "heating at 140 ℃ under normal pressure for 6 h".

Example 22:

compared with example 2, the addition amount of CHP was changed to 1g in the present example.

Example 23:

most of them were the same as in example 2, except that the amount of CHP added was changed to 2g in this example.

Example 24:

compared with example 2, the same is true for the most part, except that in this example, a solution of trimesic acid in N, N-dimethylformamide (0.025 mol. L)^-1) The amount of (2) was changed to 40 mL.

Example 25:

and embodiments thereof2 compared to the original one, the majority of the solutions were identical except that in this example, a solution of trimesic acid in N, N-dimethylformamide (0.025 mol. L)^-1) The amount of (2) was changed to 50 mL.

Example 26:

compared with example 2, most of them are the same except that in this example, "after stirring at 25 ℃ for 1 hour" is changed to "after stirring at 20 ℃ for 1 hour".

Example 27:

most of them were the same as in example 2, except that "after stirring at 25 ℃ for 1 hour" was changed to "after stirring at 40 ℃ for 1 hour" in this example.

Example 28:

compared with example 2, most of them are the same except that in this example, "after stirring at 25 ℃ for 1 hour" is changed to "after stirring at 25 ℃ for 2 hours".

Example 29:

compared with example 2, most of them are the same except that in this example, "after stirring at 25 ℃ for 1 hour" is changed to "after stirring at 25 ℃ for 3 hours".

Example 30:

compared with example 3, most of the same except that in this example, CHP @ Cu₃(BTC)₂The amount of the added material was changed to 0.1 g.

Example 31:

compared with example 3, most of the same except that in this example, CHP @ Cu₃(BTC)₂The amount of the added material was changed to 0.3 g.

Example 32:

compared with example 3, most of them are the same except that in this example, "stirring at 25 ℃ for 24 hours" is changed to "stirring at 20 ℃ for 24 hours".

Example 33:

compared with example 3, most of them are the same except that in this example, "stirring at 25 ℃ for 24 hours" is changed to "stirring at 40 ℃ for 24 hours".

Example 34:

compared with example 3, most of them are the same except that in this example, "stirring at 25 ℃ for 24 hours" is changed to "stirring at 25 ℃ for 12 hours".

Example 35:

compared with example 3, most of them are the same except that in this example, "stirring at 25 ℃ for 24 hours" is changed to "stirring at 25 ℃ for 36 hours".

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A preparation method of a metal organic framework-Cu nanometer material for an electrochemical sensor is characterized by comprising the following steps:

(2) dispersing the obtained CHP in deionized water, adding N, N-dimethylformamide solution of trimesic acid, reacting, centrifuging, washing and drying to obtain CHP @ Cu₃(BTC)₂A material;

(3) taking the obtained CHP @ Cu₃(BTC)₂Dispersing the material in anhydrous ether, adding 2, 5-dimercaptothiadiazole, reacting, centrifuging, washing and drying to obtain the target product.

2. The method for preparing the metal organic framework-Cu nanomaterial for the electrochemical sensor according to claim 1, wherein in the step (1), the copper source is copper acetate;

in the step (1), the adding amount ratio of the copper source, the deionized water and the phosphoric acid is (2-4) g: 80mL of: (0.4-0.6) mL;

in the step (1), the reaction temperature is 120-160 ℃, and the reaction time is 2-6 h.

3. The method for preparing a metal organic framework-Cu nanomaterial for an electrochemical sensor according to claim 1, wherein in the step (2), the concentration of the N, N-dimethylformamide solution of trimesic acid is 0.025 mol-L^-1And the addition amount ratio of the CHP, the deionized water and the N, N-dimethylformamide solution of the trimesic acid is (1-2) g: 51mL of: (40-50) mL;

in the step (2), the reaction temperature is 20-40 ℃, and the reaction time is 1-3 h;

in the step (2), before the reaction, the pH of the mixed solution obtained after adding the N, N-dimethylformamide solution of trimesic acid is adjusted to 6.

4. The method for preparing a metal organic framework-Cu nanomaterial for an electrochemical sensor according to claim 1, wherein in the step (3), CHP @ Cu₃(BTC)₂The adding amount ratio of the material, the anhydrous ether and the 2, 5-dimercaptothiadiazole is (0.1-0.3) g, 20mL (50-150) mg;

in the step (3), the reaction temperature is 20-40 ℃, and the reaction time is 12-36 h.

5. A metal organic framework-Cu nanomaterial for an electrochemical sensor, characterized in that the nanomaterial is prepared by the method according to any one of claims 1 to 4.

6. The use of the metal-organic framework-Cu nanomaterial for an electrochemical sensor according to claim 5, wherein the metal-organic framework-Cu nanomaterial is used for detecting heavy metal ions, and the detection process comprises the following steps:

s1: dispersing a metal organic framework-Cu nano material in a solvent to obtain a mixed solution;

7. The use of the metal-organic framework-Cu nanomaterial for an electrochemical sensor according to claim 6, wherein the heavy metal ions are lead ions.

8. The use of the metal-organic framework-Cu nanomaterial for electrochemical sensors according to claim 6, wherein in step S1, the solvent is a mixture of chitosan solution and ethanol, and the volume ratio of the chitosan solution to the ethanol is 1: 1.

9. the use of the metal-organic framework-Cu nanomaterial for electrochemical sensor according to claim 6, wherein the drop amount of the mixed solution in step S2 is 0.57-1.13 μ L/mm²。

10. The application of the metal organic framework-Cu nanomaterial for the electrochemical sensor according to claim 6, wherein in step S3, in the electrodeposition process, the voltage is-1.3 to-0.8V, and the deposition time is 130 to 330S;

in the step S3, the pH value of the acetic acid-sodium acetate buffer solution is 4-6;

in step S3, during the test of the dissolution peak current, the potential scan range is-1.0V-0V.