CN111289594A - Lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof - Google Patents

Lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof Download PDF

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CN111289594A
CN111289594A CN202010229528.1A CN202010229528A CN111289594A CN 111289594 A CN111289594 A CN 111289594A CN 202010229528 A CN202010229528 A CN 202010229528A CN 111289594 A CN111289594 A CN 111289594A
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walled carbon
carbon nanotube
lanthanum hydroxide
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于金刚
邹娇
袁萌萌
陈晓青
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Central South University
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Abstract

The invention provides a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material modified glassy carbon electrode and application thereof. The electrode comprises a glassy carbon electrode and a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material coating coated on the glassy carbon electrode; the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid is dripped on the surface of a glassy carbon electrode, and the glassy carbon electrode modified by the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material is obtained after air drying. The electrode effectively utilizes the catalytic activity of lanthanum hydroxide, the high conductivity of the oxidized multi-walled carbon nano-tube and the synergistic effect between the lanthanum hydroxide and the oxidized multi-walled carbon nano-tube, and can realize the high-sensitivity, high-stability and selective detection of the p-nitrophenol in the actual samples of the waste water of the continental plant and the water of Xiangjiang river. The method is used for quickly detecting the p-nitrophenol and has the advantages of high accuracy, high sensitivity, good selectivity, simplicity and convenience in operation and the like.

Description

Lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof
Technical Field
The invention relates to the technical field of electrochemistry, and particularly relates to a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof.
Background
Phenol is a ubiquitous environmental pollutant that has some biological toxicity. Of these, p-nitrophenol (p-NP) is the most toxic phenol and is classified as a hazard and priority pollutant by the U.S. environmental protection agency (USEPA). Due to its high stability, p-NP is difficult to degrade and is widely present in soil and aquatic environments. Unfortunately, p-NP is toxic to humans and animals, and the presence of even small amounts of p-NP can cause severe damage to the liver and kidneys. Therefore, the method for rapidly and accurately detecting the p-NP in the soil and water environment has important significance.
Rare earth elements have similar chemical properties to alkaline earth elements. Lanthanum (La) ions have higher electrical conductivity than other rare earth elements due to their smaller ionic radius. La is used alone or in combination with other elements as a highly efficient catalyst, and can be used in the fields of glass, electronics industry, ceramics, high temperature alloys and the like. In particular, La salts (such as lanthanum hydroxide) have excellent optical, electrical, and magnetic properties due to cation vacancies. Meanwhile, due to the stability and excellent catalytic activity of the sensor, the stability and the catalytic performance of the sensor can be improved by applying the La salt to the modification of the surface of the glassy carbon electrode. In addition, La-based composites also have received much attention due to their excellent photocatalytic activity towards phenol, however, La-based sensors have relatively poor electrical conductivity, limiting their widespread use as sensor platforms. Therefore, various conductive materials are compounded into the La salt to improve the conductivity and sensitivity of the sensor.
Among various conductive materials, carbon-based nanomaterials such as Graphene Nanoplatelets (GNPs), Carbon Nanotubes (CNTs), GO, etc. are widely used due to their high conductivity and large specific surface area. Among them, multi-walled carbon nanotubes (MWCNTs) have excellent electrical conductivity, extremely high mechanical strength, excellent electrocatalytic activity, and a large specific surface area, and are often used for modified electrodes. However, MWCNTs have poor dispersibility in water, and a delamination phenomenon occurs, which causes problems such as poor stability and poor reproducibility of a modified electrode. In order to improve the stability and reproducibility of the modified electrode, the advantage that the MWCNTs are rich in oxygen-containing functional groups on the surface and the tail end is fully utilized, and the oxidized carbon nanotubes (OxMWCNTs) with good dispersibility can be obtained through oxidation treatment, so that convenience is provided for manufacturing a novel carbon nanotube-based electrochemical sensor with higher stability to detect p-NP.
The current research shows that the catalytic performance of the modified electrode on p-NP can be effectively improved by applying carbon-based nano materials, metal oxides, noble metal nano particles, conductive polymers and other materials to the modified glassy carbon electrode. In order to further improve the stability, reproducibility and sensitivity of the catalytic p-NP of the sensor, the continuous development of modified materials is still necessary for the construction of the sensor.
Disclosure of Invention
The invention provides a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof, aiming at effectively improving the electrochemical current response stability and reproducibility of the modified electrode and effectively improving the detection capability of the modified electrode on p-NP.
In order to achieve the above object, an embodiment of the present invention provides a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode, which includes a glassy carbon electrode and a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite coating coated on a surface of the glassy carbon electrode.
The embodiment of the invention also provides a preparation method of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode, which comprises the following steps:
step 1, preparing rod-like lanthanum hydroxide nanoparticle dispersion liquid by taking lanthanum chloride and sodium hydroxide as raw materials;
step 2, oxidizing the multi-walled carbon nanotubes to prepare oxidized multi-walled carbon nanotube dispersion liquid;
step 3, obtaining a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid by the aid of the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid and the oxidized multi-walled carbon nanotube dispersion liquid in a self-assembly mode;
and 4, dripping the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid on the surface of the glassy carbon electrode, and airing to obtain the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode.
Preferably, the preparation process of the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid is as follows:
step 11, 5.0-20.0 mL of the solution with the concentration of 5.0-20.0 mmol L-1The lanthanum chloride solution is put into a stainless steel high-pressure reaction kettle, and 0 is added.01-0.1 mL of 1.0-10.0 mol L-1Carrying out hydrothermal reaction on the sodium hydroxide solution at the temperature of 130-180 ℃ for 3-8 h;
step 12, after the reaction is finished, after the high-pressure reaction kettle is naturally cooled to room temperature, centrifuging the mixture, washing the mixture for 2-4 times by using ultrapure water, and collecting precipitates;
step 13, dispersing the precipitate in ultrapure water to obtain 1.0mmol L-1Storing the high concentration dispersion in a refrigerator at 4 ℃ for later use;
and step 14, taking the high-concentration dispersion liquid, and diluting the high-concentration dispersion liquid by ten times with ultrapure water to obtain the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid.
Preferably, the preparation process of the oxidized multi-walled carbon nanotube dispersion liquid is as follows:
step 21, adding 15.0-35.0 mL of concentrated nitric acid and 0.2-0.4 g of potassium permanganate into 100.0-250.0 mg of multi-walled carbon nanotubes, performing ultrasonic mixing to mix the nitric acid and the potassium permanganate uniformly, and performing oil bath reaction for 3-7 hours at the temperature of 90-130 ℃ under magnetic stirring;
step 22, after the reaction is finished, adding excessive sodium sulfite to remove the residual potassium permanganate after the mixture is cooled to room temperature;
step 23, performing suction filtration and washing on the mixture, collecting a filter cake when the filtrate is neutral, dispersing the filter cake in 3.0-10.0 mL of ultrapure water, and performing vacuum freeze drying at-50 ℃ to obtain oxidized multiwalled carbon nanotube powder;
and 24, taking 2.0-5.0 mg of oxidized multi-walled carbon nanotubes in 2.0-5.0 mL of ultrapure water, and carrying out ultrasonic treatment for 3min to obtain an oxidized multi-walled carbon nanotube dispersion liquid.
Preferably, in the step 3, the self-assembly mode is ultrasonic self-assembly or hydrothermal self-assembly.
Preferably, in the step 4, the volume usage amount of the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite dispersion liquid is 3-10 μ L.
Preferably, in the step 4, one or more modes of air, nitrogen flow and infrared lamp are adopted for drying, and the drying time is 20-60 min.
The embodiment of the invention also provides a method for detecting p-nitrophenol in an actual sample, which comprises the steps of taking the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode as a working electrode, taking a platinum wire electrode as a counter electrode, taking an Ag/AgCl electrode as a reference electrode, and detecting the p-nitrophenol in an electrolyte solution and the actual sample.
Preferably, the actual samples are the waste water of the Tazhou industrial production and the Xiangjiang water.
Preferably, the electrolyte solution is one or more of inorganic salt and inorganic acid buffer solution.
The scheme of the invention has the following beneficial effects: the invention provides a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof, wherein the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode utilizes the catalytic activity of lanthanum hydroxide and oxidized multi-walled carbon nanotubes with large specific surface area and high electron mobility to realize high-sensitivity detection of p-nitrophenol in actual samples of waste water in the continental plant industry and Hunan river water. Meanwhile, based on the synergistic effect between the two materials, when the prepared glassy carbon electrode is used for electrochemically detecting p-nitrophenol, stable current response can be obtained, and a good catalytic application prospect for p-nitrophenol is shown. The adopted lanthanum hydroxide and oxidized multi-wall carbon nanotube material has the advantages of no toxicity, good stability, simple and convenient preparation and the like, and is expected to become a modified electrode material widely applied.
Drawings
FIG. 1 is an X-ray photoelectron spectrum (FIG. 1A), and X-ray photoelectron peak diffraction simulated analysis spectra of La3d (FIG. 1B) and O1s (FIG. 1C) of the rod-shaped lanthanum hydroxide nanoparticles of the present invention.
FIG. 2 is a scanning electron microscope image of the rod-shaped lanthanum hydroxide nanoparticles (FIG. 2A), oxidized multi-walled carbon nanotubes (FIG. 2B) and a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material (FIG. 2C) in the present invention.
Fig. 3 is a cyclic voltammogram (fig. 3A) and a linear scanning voltammogram (fig. 3B) of a bare electrode, a glassy carbon electrode modified by a carbon oxide nanotube, a glassy carbon electrode modified by lanthanum hydroxide, and a glassy carbon electrode modified by a lanthanum hydroxide-oxidized multi-walled carbon nanotube.
FIG. 4 is a calibration curve of peak current response of a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode to p-NP and different p-NP concentrations, and a linear scanning voltammogram of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode to p-NP solutions with different concentrations.
FIG. 5 shows the measurement of p-NP in the Welsh continent industrial wastewater and Xiangjiang water samples by using a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
Example 1
The preparation steps of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode in the embodiment are as follows:
10.0mL of 10.0mmol L-1The lanthanum chloride solution is put into a stainless steel high-pressure reaction kettle, and 0.05mL of L with the concentration of 5.0mol is added-1Carrying out hydrothermal reaction for 4 hours at 180 ℃ after the sodium hydroxide solution is prepared; after the reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, centrifuging the mixture, washing for 3 times by using ultrapure water, and collecting precipitates; the precipitate was dispersed in 10.0mL of ultrapure water to give 1.0mmol L-1The high concentration dispersion of (2) is stored in a refrigerator at 4 ℃ until use. Before use, 0.05mL of high-concentration dispersion liquid is diluted ten times by ultrapure water, and the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid is obtained.
Adding 100.0mg of multi-walled carbon nano-tube into a round-bottom flask, adding 15mL of concentrated nitric acid and 0.4g of potassium permanganate, performing ultrasonic mixing to mix the materials uniformly, and performing oil bath reaction for 7 hours at 90 ℃ under magnetic stirring; after the reaction is finished, the mixture is transferred to a beaker after being cooled to room temperature, and excessive sodium sulfite is added to remove the residual potassium permanganate; performing suction filtration and washing on the mixture, collecting a filter cake when the filtrate is neutral, dispersing the filter cake in 5.0mL of ultrapure water, and performing vacuum freeze drying at-50 ℃ to finally obtain oxidized multi-walled carbon nanotube powder; weighing 2.0mg of oxidized multi-walled carbon nanotubes in 3.5mL of ultrapure water, and carrying out ultrasonic treatment for 3min to obtain an oxidized multi-walled carbon nanotube dispersion liquid.
And (3) carrying out ultrasonic self-assembly on the prepared lanthanum hydroxide and oxidized multi-walled carbon nanotube dispersion liquid for 1min to obtain the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid.
Transferring 5 mu L of the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid, dripping the dispersion liquid on the surface of a glassy carbon electrode, and airing the glassy carbon electrode in an infrared lamp for 20min to obtain the nano-composite material.
Example 2
The preparation steps of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode in the embodiment are as follows:
15.0mL of 5.0mmol L-1The lanthanum chloride solution is put into a stainless steel high-pressure reaction kettle, and 0.01mL of 10.0mol L of lanthanum chloride solution is added-1Carrying out hydrothermal reaction for 4 hours at 160 ℃ after the sodium hydroxide solution is prepared; after the reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, centrifuging the mixture, washing for 3 times by using ultrapure water, and collecting precipitates; the precipitate was dispersed in 10.0mL of ultrapure water to give 1.0mmol L-1The high concentration dispersion of (2) is stored in a refrigerator at 4 ℃ until use. Before use, 0.1mL of high-concentration dispersion liquid is diluted ten times by ultrapure water, and the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid is obtained.
Adding 200.0mg of multi-walled carbon nano-tube into a round-bottom flask, adding 20mL of concentrated nitric acid and 0.5g of potassium permanganate, performing ultrasonic mixing to mix the materials uniformly, and performing oil bath reaction for 6 hours at the temperature of 100 ℃ under magnetic stirring; after the reaction is finished, the mixture is transferred to a beaker after being cooled to room temperature, and excessive sodium sulfite is added to remove the residual potassium permanganate; performing suction filtration and washing on the mixture, collecting a filter cake when the filtrate is neutral, dispersing the filter cake in 10.0mL of ultrapure water, and performing vacuum freeze drying at-50 ℃ to finally obtain oxidized multi-walled carbon nanotube powder; weighing 2.0mg of oxidized multi-walled carbon nanotubes in 5.0mL of ultrapure water, and performing ultrasonic treatment for 3min to obtain an oxidized multi-walled carbon nanotube dispersion liquid.
And carrying out hydrothermal self-assembly on the prepared lanthanum hydroxide and oxidized multi-walled carbon nanotube dispersion liquid for 10min at 50 ℃ to obtain the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid.
And transferring 9 mu L of the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid, dripping the dispersion liquid on the surface of the glassy carbon electrode, and airing the glassy carbon electrode in the air for 60min to obtain the nano-composite material.
Example 3
The preparation steps of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode in the embodiment are as follows:
20.0mL of 10.0mmol L-1The lanthanum chloride solution is put into a stainless steel high-pressure reaction kettle, and 0.1mL of L with the concentration of 3.0mol is added-1Carrying out hydrothermal reaction for 7 hours at 130 ℃ after the sodium hydroxide solution is prepared; after the reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, centrifuging the mixture, washing for 3 times by using ultrapure water, and collecting precipitates; the precipitate was dispersed in 10.0mL of ultrapure water to give 1.0mmol L-1The high concentration dispersion of (2) is stored in a refrigerator at 4 ℃ until use. Before use, 0.15mL of high-concentration dispersion liquid is diluted ten times by ultrapure water, and the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid is obtained.
Adding 150.0mg of multi-walled carbon nano-tube into a round-bottom flask, adding 25.0mL of concentrated nitric acid and 0.2g of potassium permanganate, performing ultrasonic mixing to mix uniformly, stirring by magnetic force, and performing oil bath reaction at 120 ℃ for 4 hours; after the reaction is finished, the mixture is transferred to a beaker after being cooled to room temperature, and excessive sodium sulfite is added to remove the residual potassium permanganate; performing suction filtration and washing on the mixture, collecting a filter cake when the filtrate is neutral, dispersing the filter cake in 6.0mL of ultrapure water, and performing vacuum freeze drying at-50 ℃ to finally obtain oxidized multi-walled carbon nanotube powder; weighing 4.0mg of oxidized multi-walled carbon nanotubes in 2.5mL of ultrapure water, and performing ultrasonic treatment for 3min to obtain an oxidized multi-walled carbon nanotube dispersion liquid.
And (3) carrying out ultrasonic self-assembly on the prepared lanthanum hydroxide and oxidized multi-walled carbon nanotube dispersion liquid for 5min to obtain the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid.
And transferring 7 mu L of the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid, dripping the dispersion liquid on the surface of the glassy carbon electrode, and airing the glassy carbon electrode for 30min in nitrogen flow to obtain the nano-composite material.
Example 4
The preparation steps of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode in the embodiment are as follows:
10.0mL of 15.0mmol L-1The lanthanum chloride solution is put into a stainless steel high-pressure reaction kettle, and 0.05mL of L with the concentration of 8.0mol is added-1Carrying out hydrothermal reaction for 5 hours at 150 ℃ after the sodium hydroxide solution is prepared; after the reaction is finished, naturally cooling the high-pressure reaction kettle to room temperature, centrifuging the mixture, washing for 3 times by using ultrapure water, and collecting precipitates; the precipitate was dispersed in 10.0mL of ultrapure water to give 1.0mmol L-1The high concentration dispersion of (2) is stored in a refrigerator at 4 ℃ until use. Before use, 0.1mL of high-concentration dispersion liquid is diluted ten times by ultrapure water, and the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid is obtained.
Adding 300.0mg of multi-walled carbon nano-tube into a round-bottom flask, adding 30.0mL of concentrated nitric acid and 0.5g of potassium permanganate, performing ultrasonic mixing to mix uniformly, stirring by magnetic force, and performing oil bath reaction for 5 hours at 110 ℃; after the reaction is finished, the mixture is transferred to a beaker after being cooled to room temperature, and excessive sodium sulfite is added to remove the residual potassium permanganate; performing suction filtration and washing on the mixture, collecting a filter cake when the filtrate is neutral, dispersing the filter cake in 8.0mL of ultrapure water, and performing vacuum freeze drying at-50 ℃ to finally obtain oxidized multi-walled carbon nanotube powder; 5.0mg of oxidized multi-walled carbon nanotubes are weighed in 5mL of ultrapure water, and ultrasonic treatment is carried out for 3min to obtain oxidized multi-walled carbon nanotube dispersion liquid.
And carrying out hydrothermal self-assembly on the prepared lanthanum hydroxide and oxidized multi-walled carbon nanotube dispersion liquid for 5min at 50 ℃ to obtain the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid.
Transferring 8 mu L of the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid, dripping the dispersion liquid on the surface of a glassy carbon electrode, and airing the glassy carbon electrode in an infrared lamp for 30min to obtain the nano-composite material.
Example 5
The glassy carbon electrode modified by the lanthanum hydroxide-oxidized multi-walled carbon nanotube obtained in example 1 was used for detection:
verification of successful Synthesis of La (OH) by X-ray photoelectron Spectroscopy (XPS)3And (3) nanoparticles. As shown in FIGS. 1A and 2A, La (OH)3The XPS scanning spectrum of (A) has a signature, indicating the presence of La and O elements. At the same time, also pairXPS peak diffraction simulation analysis was performed on La and O elements to further confirm the valence states of La and O elements. As can be seen from FIG. 1B, La (OH)3The diffraction simulation analysis spectrum of the La3d peak is consistent with that reported in the prior literature, and 3dcf in the figure0And 3dcf1Respectively representing the no-charge and charge-transfer states. And 3dcf1In contrast, 3dcf0The higher peak intensity of (a) is due to the increase in orbital binding energy. Wherein, the binding energy of the two peaks is 835.0eV and 852.0eV which respectively correspond to La3d5/2And La3d3/2This may be related to hydroxides. This sample showed four characteristic peaks, La3d5/2Middle 3dcf1And 3dcf0The difference in binding energy (. DELTA.E) between them was 3.9eV, which corresponds to La (III). In addition, the diffraction simulation analysis of the O1s peak is also shown in FIG. 1C, and a sharp and symmetrical peak appears at the binding energy of 530.3eV, which is attributed to the presence of lanthanum-oxygen bond (La-O). Thus, the XPS results confirm that La (OH)3The successful preparation.
Compared with the existing glassy carbon electrode, the electrode prepared by the method is based on the synergistic effect between the lanthanum hydroxide and the oxidized multi-walled carbon nanotube, and has high catalytic activity and selectivity. By utilizing the catalytic activity of the lanthanum hydroxide, target molecules can be catalyzed efficiently; the characteristics of large specific surface area and high electron mobility of the oxidized multi-walled carbon nanotube (shown in figure 2B) are fully utilized, so that the enrichment degree of a substance to be detected around the electrode is improved, the electron transfer rate between the electrolyte and the electrode is accelerated, stable current response is obtained when the prepared glassy carbon electrode is used for electrochemically detecting p-nitrophenol, the catalytic efficiency is improved, and the reaction efficiency is accelerated.
According to the preparation method, lanthanum hydroxide with excellent catalytic performance is synthesized and used for modifying the electrode, so that the interface catalytic capability can be effectively improved; meanwhile, the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material (figure 2C) is prepared by utilizing the excellent conductivity of the oxidized multi-walled carbon nanotube and the self-assembly of lanthanum hydroxide, so that the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode is obtained, the effective surface area of the electrode is increased and the enrichment of an object to be detected on the surface of the electrode is improved due to the synergistic effect between the lanthanum hydroxide and oxidized multi-walled carbon nanotube modified glassy carbon electrode, and the good conductivity and catalytic property of the sensor are ensured.
Taking the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode prepared in example 1 as a working electrode, a platinum wire electrode as a counter electrode and an Ag/AgCl electrode as a reference electrode, measuring p-nitrophenol in a 0.1M phosphoric acid buffer solution with the pH value of 7.0, and selecting the waste water from the Taoisia industry and the Xiangjiang water as actual samples for separation, wherein the detection results are as follows:
at 0.1mol L by Cyclic Voltammetry (CV)-130.0. mu. molL of phosphate buffer solution at pH 7.0-1p-NP is at bare electrode (bareGCE), oxidized carbon nanotube modified glassy carbon electrode (OxMWCNTs/GCE), lanthanum hydroxide modified glassy carbon electrode (La (OH)3/GCE) and lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode (La (OH)3-OxMWCNTs/GCE). As shown in FIG. 3A, the CV plot for p-NP shows one oxidation peak and two reduction peaks. In the present invention, only the oxidation peak was examined, and it can be observed from FIG. 3A that the use of bareGCE, La (OH)3Per GCE, OxMWCNTs/GCE and La (OH)330.0. mu. mol L of-OxMWCNTs/GCE-1The p-NP of (2) showed a distinct oxidation peak at 0.13V, and the oxidation peak current was gradually increased with current responses of 0.81. mu.A, 1.06. mu.A, 1.96. mu.A and 2.86. mu.A, respectively. Interestingly, La (OH)3The highest oxidation peak current was obtained for-OxMWCNTs/GCE, which indicates that La (OH)3The electrochemical detection of p-NP by-OxMWCNTs/GCE shows better electrocatalytic capability. In addition, the voltage was also measured at 0.1mol L by Linear Sweep Voltammetry (LSV)-130.0. mu. mol L of phosphate buffer solution with pH 7.0-1The electrochemical behavior of p-NPs on the above-mentioned electrodes. As shown in FIG. 3B, the oxidation peak currents of p-NP were in bareGCE, La (OH), respectively3/GCE、OxMWCNTs/GCE、La(OH)3the-OxMWCNTs/GCE showed a significant increase, with oxidation peak current responses of 1.63. mu.A, 1.84. mu.A, 5.71. mu.A and 16.73. mu.A, respectively. Likewise, in La (OH)3The highest oxidation peak current response is shown on OxMWCNTs/GCE, the peak current responses are OxMWCNTs/GCE, La (OH)32.9, 9.1 and 10.3 times of/GCE and bareGCE. It follows that the significant increase in peak current is attributable to the excellent electrocatalytic activity,High electrical conductivity and La (OH)3And OxMWCNTs. Importantly, LSVs have a higher current response and better peak shape than CVs. Thus, the LSV method was used to determine p-NP in a linear experiment.
By LSV, with La (OH)3The determination concentration of-OxMWCNTs/GCE is 1.0-30.0 mu mol L-1p-NP of (2). As shown in FIG. 4, the oxidation peak current increased from 1.0 to 30.0. mu. mol L with the p-NP concentration-1Gradually increases, and shows a good linear relation between the peak current and the concentration, and the linear regression equation is that Ipa (mu A) is 0.50Cp-NP(μmol L-1)-0.11(R20.9971). The detection Limit (LOD) was calculated to be 0.27. mu. mol L from the 3-fold signal-to-noise ratio-1. Visible La (OH)3The sensitivity of the-OxMWCNTs/GCE to p-NP is high, the manufacturing process is relatively simple and convenient, and the potential application prospect of the-OxMWCNTs/GCE as a novel La-base sensor is shown.
To verify La (OH)3Potential application of-OxMWCNTs/GCE, p-NP in practical samples such as Tazhou industrial wastewater and Hunan river water is determined. Before use, 0.1mol L of waste water from the Tanzhou industry is used-1The pH value is 100 times of the dilution of the phosphoric acid buffer solution with 7.0. Then passed through a labeling experiment using La (OH)3-OxMWCNTs/GCE is used for determining the content of p-NP in the waste water of Tazhou industrial production and Hunan river water. As can be seen from FIG. 5, both the waste water from the Tanshou industry and the Hunan river water do not contain p-NP, and the recovery rate and the Relative Standard Deviation (RSD) of the p-NP are respectively between 95.62-110.75% and 1.65-3.85%. These results show that La (OH)3the-OxMWCNTs/GCE has the advantages of high accuracy, good stability, strong anti-interference capability and the like.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. The lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode is characterized by comprising a glassy carbon electrode and a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material coating coated on the surface of the glassy carbon electrode.
2. The preparation method of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode as claimed in claim 1, characterized by comprising the following steps:
step 1, preparing rod-like lanthanum hydroxide nanoparticle dispersion liquid by taking lanthanum chloride and sodium hydroxide as raw materials;
step 2, oxidizing the multi-walled carbon nanotubes to prepare oxidized multi-walled carbon nanotube dispersion liquid;
step 3, obtaining a lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid by the aid of the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid and the oxidized multi-walled carbon nanotube dispersion liquid in a self-assembly mode;
and 4, dripping the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite material dispersion liquid on the surface of the glassy carbon electrode, and airing to obtain the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode.
3. The method for preparing the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode as claimed in claim 2, wherein the preparation process of the rod-like lanthanum hydroxide nanoparticle dispersion liquid is as follows:
step 11, 5.0-20.0 mL of the solution with the concentration of 5.0-20.0 mmol L-1The lanthanum chloride solution is put into a stainless steel high-pressure reaction kettle, and 0.01-0.1 mL of L with the concentration of 1.0-10.0 mol is added-1Carrying out hydrothermal reaction on the sodium hydroxide solution at the temperature of 130-180 ℃ for 3-8 h;
step 12, after the reaction is finished, after the high-pressure reaction kettle is naturally cooled to room temperature, centrifuging the mixture, washing the mixture for 2-4 times by using ultrapure water, and collecting precipitates;
step 13, dispersing the precipitate in ultrapure water to obtain 1.0mmol L-1Storing the high concentration dispersion in a refrigerator at 4 ℃ for later use;
and step 14, taking the high-concentration dispersion liquid, and diluting the high-concentration dispersion liquid by ten times with ultrapure water to obtain the rod-shaped lanthanum hydroxide nanoparticle dispersion liquid.
4. The method for preparing a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode according to claim 3, wherein the oxidized multi-walled carbon nanotube dispersion liquid is prepared by the following steps:
step 21, adding 15.0-35.0 mL of concentrated nitric acid and 0.2-0.4 g of potassium permanganate into 100.0-250.0 mg of multi-walled carbon nanotubes, performing ultrasonic mixing to mix the nitric acid and the potassium permanganate uniformly, and performing oil bath reaction for 3-7 hours at the temperature of 90-130 ℃ under magnetic stirring;
step 22, after the reaction is finished, adding excessive sodium sulfite to remove the residual potassium permanganate after the mixture is cooled to room temperature;
step 23, performing suction filtration and washing on the mixture, collecting a filter cake when the filtrate is neutral, dispersing the filter cake in 3.0-10.0 mL of ultrapure water, and performing vacuum freeze drying at-50 ℃ to obtain oxidized multiwalled carbon nanotube powder;
and 24, taking 2.0-5.0 mg of oxidized multi-walled carbon nanotubes in 2.0-5.0 mL of ultrapure water, and carrying out ultrasonic treatment for 3min to obtain an oxidized multi-walled carbon nanotube dispersion liquid.
5. The method for preparing a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode according to claim 4, wherein in the step 3, the self-assembly mode is ultrasonic self-assembly or hydrothermal self-assembly.
6. The method for preparing a glassy carbon electrode modified by lanthanum hydroxide-oxidized multi-walled carbon nanotubes in claim 5, wherein in the step 4, the volume usage amount of the lanthanum hydroxide-oxidized multi-walled carbon nanotube composite dispersion liquid is 3-10 μ L.
7. The preparation method of the lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode according to claim 6, wherein in the step 4, one or more modes of air, nitrogen flow and infrared lamp are adopted for air drying, and the air drying time is 20-60 min.
8. A method for detecting p-nitrophenol in an actual sample, which is characterized in that a lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode prepared by the method of claims 2 to 8 is used as a working electrode, a platinum wire electrode is used as a counter electrode, an Ag/AgCl electrode is used as a reference electrode, and the p-nitrophenol in an electrolyte solution and the actual sample is detected.
9. The method according to claim 8, wherein the actual samples are waste water from the Tabar industry and Hunan river water.
10. The method according to claim 9, wherein the electrolyte solution is one or more of an inorganic salt and an inorganic acid buffer solution.
CN202010229528.1A 2020-03-27 2020-03-27 Lanthanum hydroxide-oxidized multi-walled carbon nanotube modified glassy carbon electrode and application thereof Pending CN111289594A (en)

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