CN108398468B - Preparation method of carbon paste electrode modified based on covalent organic framework material - Google Patents
Preparation method of carbon paste electrode modified based on covalent organic framework material Download PDFInfo
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Abstract
A preparation method based on covalent organic framework material modified carbon paste electrode relates to the technical field of electrochemical sensors, and comprises the steps of dissolving 1,3, 5-tri (4-aminophenylbenzene) and 2, 5-dimethoxyterephthalaldehyde in a solvent, and reacting under the catalysis of acetic acid to obtain TAPB-DMTP-COF; mixing and grinding TAPB-DMTP-COF and graphite powder, and then mixing with paraffin oil to obtain a mixture; and pressing the mixture into a polytetrafluoroethylene tube, and inserting a lead to prepare the covalent organic framework material-based modified carbon paste electrode. The electrochemical sensor is constructed and used for detecting lead, and the TAPB-DMTP-COF is modified to a carbon paste electrode, so that the current response to the lead is improved.
Description
Technical Field
The invention relates to the technical field of electrochemical sensors, in particular to a preparation method of a TAPB-DMTP-COF modified carbon paste electrode, and the modified electrode is used for detecting lead by using a differential pulse stripping voltammetry method.
Background
Lead is a heavy metal which has great harm to human body, is widely distributed in the atmosphere, water, soil and organisms, and can be accumulated in the human body through a food chain, thereby affecting the health of human body. Because metallic lead has the characteristics of difficult degradation and high neurotoxicity, nervous system injury, brain injury, anemia, reproductive system disorder, renal failure and the like can be caused by long-term exposure to high-concentration lead. Not to be neglected, lead can cause children's mental retardation and affect children's healthy growth. Therefore, it is of great significance to develop a rapid and sensitive analysis method for quantitatively detecting lead.
At present, some analysis methods such as atomic absorption spectrometry, atomic emission spectrometry, inductively coupled plasma spectrometry, gas chromatography and the like are used for detecting the content of lead, and although these methods have the advantages of high sensitivity, good selectivity and the like, these methods have the disadvantages of tedious pretreatment procedure, time consumption, high cost and the like.
The covalent organic framework material is a crystalline porous material formed by covalent bonding by taking an organic precursor as a building unit, and compared with an MOF material, the COF has higher chemical stability and lower density. The COF has high stability, structural regularity, pore adjustability and easy functionality, so that the COF is applied to the fields of gas storage, drug release, catalysis, electrochemistry and the like. The TAPB-DMTP-COF has the characteristics of high crystallinity, porosity, large specific surface area and the like, so that the TAPB-DMTP-COF is expected to be an electrode material for electrochemical sensing application due to the unique properties.
Disclosure of Invention
In order to solve the problems, the invention provides a high specific surface area (2422 m)2The covalent organic framework material of/g) is used as an electrode material, the material modified carbon paste electrode can effectively detect the content of heavy metal lead, and the sensor has the advantages of simple manufacture, quick detection and high sensitivity.
The invention comprises the following steps:
1) dissolving 1,3, 5-tri (4-aminophenyl benzene) and 2, 5-dimethoxyterephthalaldehyde in a solvent under the ultrasonic condition, and reacting under the catalysis of acetic acid to obtain TAPB-DMTP-COF;
the reaction formula is as follows:
2) mixing and grinding TAPB-DMTP-COF and graphite powder, and then mixing with paraffin oil to obtain a mixture; and pressing the mixture into a polytetrafluoroethylene tube, and inserting a lead to prepare the covalent organic framework material-based modified carbon paste electrode.
The electrochemical sensor is constructed and used for detecting lead, and the TAPB-DMTP-COF is modified to a carbon paste electrode, so that the current response to the lead is improved. The TAPB-DMTP-COF has a large specific surface area and a porous structure, so that the concentration of lead enriched on the surface of an electrode is improved, the detection range of the sensor on the lead is 0.01-2 mu M, the detection limit is 0.0044 mu M, and the sensor has the advantages of high sensitivity, good selectivity and good reproducibility.
Further, in the step 1) of the present invention, the mixing molar ratio of the 1,3, 5-tris (4-aminophenylbenzene) and the 2, 5-dimethoxyterephthalaldehyde is 2: 3. The reaction mechanism is that amino and aldehyde group react to generate imine bond, 1 mole of 1,3, 5-tri (4-aminophenyl benzene) corresponds to 3 moles of amino, 1 mole of 2, 5-dimethoxyterephthalaldehyde corresponds to 2 moles of aldehyde group, and the aldehyde group and the amino group are reacted in a ratio of 1:1, so that the mixing molar ratio of the 1,3, 5-tri (4-aminophenyl benzene) and the 2, 5-dimethoxyterephthalaldehyde is 2: 3.
In the step 1), the solvent is formed by mixing 1, 4-dioxane, n-butanol and methanol according to the volume ratio of 4: 1. The two monomers have low solubility, the solvent is too little, the monomers are not easy to dissolve, and the monomers are just completely dissolved in the ratio.
In the step 1), the concentration of the acetic acid is 12 moL/L. The formation of COF materials mainly includes the following two processes: one is the aggregation process; one is an ordered arrangement process. Good crystalline materials can be obtained only by properly controlling the aggregation speed and the arrangement speed of the materials, the concentration of acetic acid is too high, the aggregation speed is too high, disordered arrangement can be caused, the concentration of the acetic acid is too low, the reaction rate is too slow, incomplete crystallization can be caused, amorphous materials are generated, and therefore the concentration of acid added in the process of synthesizing the materials cannot be too high or too low.
In the step 1), the reaction is firstly carried out for 2 hours at room temperature under the catalysis of acetic acid, then the acetic acid is added again, and the reaction is carried out for 24 hours after the temperature is raised to 70 ℃. The reaction is firstly slowly polymerized to generate amorphous polymer at room temperature, and then the assembly rearrangement is generated at high temperature to form high-crystalline polymer.
In the step 1), the precipitate generated in the reaction is washed with tetrahydrofuran and acetone, and then dried in vacuum to obtain a TAPB-DMTP-COF solid. Since the reaction is reversible and there is a possibility of oligomer formation, the oligomers are washed off with tetrahydrofuran and acetone.
In the step 2), the mixing mass ratio of the graphite powder to the TAPB-DMTP-COF is 7: 1. If the content of TAPB-DMTP-COF is too small, the specific surface area of the electrode surface is not increased remarkably, the adsorption amount of lead ions cannot be increased remarkably, and if the content of TAPB-DMTP-COF is too high, electron transfer is hindered and the response to lead ions is reduced due to poor conductivity of TAPB-DMTP-COF.
Drawings
FIG. 1 is an X-ray powder diffraction pattern of the covalent organic framework material described in example 1 of the present invention.
FIG. 2 is a scanning electron micrograph of the covalent organic framework material of example 1 of the present invention.
FIG. 3 shows Pb in example 1 of the present invention2+Voltammetric plot of concentration versus peak current.
FIG. 4 shows Pb in example 1 of the present invention2+Linear regression plot of concentration versus peak current.
Detailed Description
Firstly, preparing a carbon paste electrode modified based on a covalent organic framework material:
1. preparation of TAPB-DMTP-COF:
at room temperature, 10.5 mg of 1,3, 5-tri (4-aminophenylbenzene) and 8.5 mg of 2, 5-dimethoxyterephthalaldehyde monomer are weighed and dissolved in 4.5 mL of 1, 4-dioxane, n-butanol and methanol (4:4:1 v/v/v) solution, after the monomer is dissolved by ultrasonic half an hour, 0.05 mL of acetic acid is slowly dripped, the reaction is carried out for 2h at room temperature, 0.45 mL of acetic acid is continuously dripped, and the reaction is carried out for 24h in a 70 ℃ oven. The obtained precipitate was washed with tetrahydrofuran and acetone and finally dried in vacuo for 24h to give TAPB-DMTP-COF as a yellow solid.
The X-ray powder diffraction pattern of the yellow solid is shown in figure 1. Curve 1 in FIG. 1 represents the theoretically fitted XRD and curve 2 represents the experimentally fitted XRD. As can be seen from the figure, the position of the XRD peak obtained by the experiment is consistent with the theoretical fitting, which shows that the material is successfully synthesized by the invention.
The scanning electron micrograph of the yellow solid is shown in FIG. 2, from which FIG. 2 it can be seen: the morphology of the material was uniformly spherical with a size of about 0.9 μm.
2. Preparing a TAPB-DMTP-COF modified carbon paste electrode:
weighing 0.4g of graphite powder and 0.028g of TAPB-DMTP-COF in an agate mortar at room temperature, fully grinding and uniformly mixing, then dropwise adding 0.1mL of paraffin oil, continuously grinding and uniformly mixing, pressing into a polytetrafluoroethylene tube with the inner diameter of 3mm after uniformly mixing, compacting by using a glass rod, and inserting a copper wire. After the electrode was prepared, Al having a particle size of 0.03 μm2O3And (5) polishing the middle part of the blank to be smooth, and drying the blank by using nitrogen.
Secondly, testing results:
1. soaking the electrolytic cell in 10% nitric acid for 12h, cleaning with distilled water, and drying. 10mL of 0.1M acetic acid-sodium acetate buffer (pH = 4.5) was accurately transferred to an electrolytic cell, a 1. mu.M standard solution was prepared by adding a lead standard solution, and a clean magneton was placed to mix the solution uniformly.
2. A traditional three-electrode system is adopted, a TAPB-DMTP-COF modified carbon paste electrode is used as a working electrode, an Ag/AgCl electrode is used as a reference electrode, a platinum electrode is used as a counter electrode, and the three-electrode system is connected with an electrochemical workstation.
3. The detection process of the differential pulse anodic stripping voltammetry comprises the following steps: stirring and enriching for 300s at a deposition voltage of-1.2V, turning off stirring and standing for 20s after deposition is finished, setting an initial potential of-1V, a termination potential of-0.1V, a potential increment of 0.01V, a pulse amplitude of 0.1V, a pulse width of 1.0s and a pulse interval of 0.2s, and recording a stripping voltammetry curve.
4. Repeating the steps 1, 2 and 3, preparing the lead standard solution into 0.01, 0.05, 0.1, 0.5, 0.75, 1, 1.5 and 2 mu M, recording a lead ion differential pulse anodic stripping voltammetry curve, and making a linear regression graph by using the peak current-lead concentration (obtaining figures 3 and 4).
FIG. 3 shows Pb in example 1 of the present invention2+The voltammetric plot of concentration versus peak current, as seen in fig. 3: in the process of measuring lead ions, the concentration of the lead ions is in the range of 0.01-2 mu M, and the peak current of the modified carbon paste electrode increases along with the increase of the concentration of the lead ions.
FIG. 4 shows Pb in example 1 of the present invention2+Concentration and peakLinear regression plot of current, as seen in fig. 3: in the process of measuring lead ions, the lead ion concentration of the modified carbon paste electrode is in a range of 0.01-2 mu M and has good linear relation with peak current, and the linear equation is I (mu A) = 4.7392C (mu M) +0.7592 (R)2=0.9975) and a detection limit of 0.0044 μ M (S/N = 3), and the electrochemical measurement of lead using the present invention has advantages of simple preparation, high sensitivity and low detection limit.
5. To verify the reliability of the sensor, the actual sample was tested.
Tap water and lake water samples before analysis were filtered through a 0.45 μ M filter membrane, 10mL of the treated water samples were taken, lead standard solutions (1 μ M, 2 μ M and 3 μ M) of different concentrations were added respectively by a standard addition method, peak currents of the different concentrations were recorded by the same method as in example 2, the concentration of lead ions was calculated from the working curve obtained in step 4 in example 2, and the recovery rate was calculated, with the results shown in table 1.
TABLE 1 detection of lead content in Water samples
Table 1 the results show that: the recovery rate of the modified electrode for detecting a water sample is between 97.0% and 103.0%, and the validity and reliability of the modified electrode to lead in the water sample are proved.
Claims (2)
1. A preparation method of a covalent organic framework material modified carbon paste electrode for detecting lead ions comprises the following steps:
soaking an electrolytic cell in 10% nitric acid for 12h, cleaning with distilled water, drying, accurately transferring 10mL of 0.1M, pH =4.5 acetic acid-sodium acetate buffer solution into the electrolytic cell, adding a lead standard solution to prepare a 1 mu M standard solution, and adding a clean magneton to uniformly mix the solution;
connecting a three-electrode system with an electrochemical workstation by taking a TAPB-DMTP-COF modified carbon paste electrode as a working electrode, an Ag/AgCl electrode as a reference electrode and a platinum electrode as a counter electrode;
the detection process of the differential pulse anodic stripping voltammetry comprises the following steps: stirring and enriching for 300s at a deposition voltage of-1.2V, turning off stirring and standing for 20s after deposition is finished, setting an initial potential of-1V, a final potential of-0.1V, a potential increment of 0.01V, a pulse amplitude of 0.1V, a pulse width of 1.0s and a pulse interval of 0.2s, and recording a stripping voltammetry curve;
repeating the steps, preparing lead standard solution into 0.01, 0.05, 0.1, 0.5, 0.75, 1, 1.5 and 2 mu M, recording lead ion differential pulse anode stripping voltammetry curves, and making a linear regression graph by using peak current-lead concentration;
the TAPB-DMTP-COF modified carbon paste electrode is prepared by the following steps:
1) dissolving 1,3, 5-tri (4-aminophenyl benzene) and 2, 5-dimethoxyterephthalaldehyde in a solvent under an ultrasonic condition, firstly reacting for 2 hours at room temperature under the catalysis of acetic acid, then adding acetic acid again, heating to 70 ℃, and reacting for 24 hours to obtain TAPB-DMTP-COF; the mixing molar ratio of the 1,3, 5-tri (4-aminophenyl benzene) to the 2, 5-dimethoxyterephthalaldehyde is 2: 3; the solvent is formed by mixing 1, 4-dioxane, n-butanol and methanol according to the volume ratio of 4: 1; the concentration of the acetic acid is 12 moL/L;
2) mixing and grinding TAPB-DMTP-COF and graphite powder, and then mixing paraffin oil, wherein the mixing mass ratio of the graphite powder to the TAPB-DMTP-COF is 7: 1, so as to obtain a mixture; and pressing the mixture into a polytetrafluoroethylene tube, and inserting a lead to prepare the covalent organic framework material-based modified carbon paste electrode.
2. The method according to claim 1, wherein in the step 1), the precipitate formed by the reaction is washed with tetrahydrofuran and acetone, and then dried under vacuum to obtain TAPB-DMTP-COF solid.
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| CN109280179B (en) * | 2018-11-19 | 2021-04-09 | 天罡新材料（廊坊）股份有限公司 | Covalent organic framework material, preparation method thereof and application thereof in hindered amine synthesis |
| CN109912807B (en) * | 2019-02-18 | 2021-12-10 | 山东省分析测试中心 | Preparation method and application of covalent organic framework material |
| CN109942827B (en) * | 2019-05-22 | 2022-03-01 | 武汉理工大学 | Method for modifying covalent organic framework material |
| CN110240683B (en) * | 2019-06-11 | 2020-06-19 | 山东大学 | Covalent organic framework material, preparation method thereof and application thereof in fluorescent sensor |
| CN110372068B (en) * | 2019-07-10 | 2021-07-27 | 常州大学 | Preparation method and application of COF-loaded metal hydroxide electrode |
| CN110739427B (en) * | 2019-10-18 | 2021-11-12 | 华南师范大学 | Battery diaphragm material and preparation method and application thereof |
| CN113087917B (en) * | 2021-03-05 | 2023-03-17 | 上海簇睿低碳能源技术有限公司 | 2D covalent organic framework material and preparation method and application thereof |
| CN113336907B (en) * | 2021-06-08 | 2022-11-15 | 四川大学 | Methoxy side chain-based visual pH response COFs material and preparation method and application thereof |
| CN113388129A (en) * | 2021-06-08 | 2021-09-14 | 中国石油大学(华东) | Method for quickly preparing Schiff base covalent organic framework material at low temperature and application |
| WO2024007199A1 (en) * | 2022-07-06 | 2024-01-11 | 苏州大学 | Barium titanate nanoparticle-compounded covalent organic framework heterojunction, and preparation method therefor |
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