CN110057885B

CN110057885B - A kind of gadolinium oxide nano hollow sphere modified electrode and its preparation method and electrochemical sensor and application

Info

Publication number: CN110057885B
Application number: CN201910299550.0A
Authority: CN
Inventors: 李茂国; 刘超; 蒋田
Original assignee: Anhui Normal University
Current assignee: Anhui Normal University
Priority date: 2019-04-15
Filing date: 2019-04-15
Publication date: 2021-07-02
Anticipated expiration: 2039-04-15
Also published as: CN110057885A

Abstract

The invention discloses an electrode modified by gadolinium oxide nanometer hollow spheres, a preparation method thereof, an electrochemical sensor and application thereof. The preparation method comprises the following steps: adding polydopamine spheres into an aqueous solution containing gadolinium salt and urea for mixing and contacting; Obtaining an intermediate; (2) calcining the intermediate in air at high temperature to obtain gadolinium oxide hollow spheres; (3) coating the dispersed droplets containing gadolinium oxide hollow spheres on the surface of the glassy carbon electrode, and then dripping Nafion on the surface of the glassy carbon electrode Diluent to obtain an electrode modified with gadolinium oxide nano hollow spheres. The gadolinium oxide nanometer hollow sphere modified electrode can be used for the detection of methyl parathion, and has low detection limit, good linearity, high stability and reproducibility, and strong anti-interference ability. Not only that, the preparation method of the gadolinium oxide nano hollow sphere modified electrode is simple and easy to control, and has high popularization and application value.

Description

Gadolinium oxide nano hollow sphere modified electrode, preparation method thereof, electrochemical sensor and application

Technical Field

The invention relates to an electrochemical sensor, in particular to an electrode modified by gadolinium oxide nano hollow spheres, a preparation method thereof, an electrochemical sensor and application thereof.

Background

China is a big agricultural country, pesticides are used at a high level along with the development of modern agriculture, and since a plurality of unreasonable places exist in the using process, the pesticide residues of vegetables seriously exceed the standard, and can directly endanger important organs of human bodies, such as nervous systems, livers, kidneys and the like. Meanwhile, residual pesticide is accumulated in a human body, and after a certain measure is exceeded, chronic diseases such as muscle numbness, cough and the like can be caused, and vascular diseases, diabetes, cancer and the like can be even induced. Because pesticide residues are harmful to human beings and organisms, the application of pesticides is strictly managed in various countries, and the allowable amount of pesticide residues in food is regulated. There is a greater need for techniques for detecting pesticide residues.

Methyl parathion is commonly known as methyl 1605, the scientific name of 0, 0-dimethyl-0- (4-nitrophenyl) thiophosphate, an organophosphorus insecticide. The industrial product is yellowish-brown oily liquid with garlic odor, the pure product is white crystal, the melting point is 36-36.5 ℃, the product is insoluble in water and soluble in organic solvent, the product can be isomerized by heating, and the product is easily decomposed at high temperature or under alkali. Acute toxicity LD50 values: the oral administration of the composition to white rats is 14-24mg/kg, and the transdermal administration of the composition to rabbits is 300-400 mg/kg, and the composition belongs to high-toxicity pesticides. The electrochemical sensor has wide application prospect in the detection of the phosphorus pesticide due to the characteristics of rapidness, convenience, sensitivity, easy miniaturization of a probe, small equipment and the like.

In recent years, various countries and organizations in the world have made strict restrictions on OPPs residues and show an increasingly severe trend. In order to meet the requirement of rapid separation and analysis of trace or even ultra-trace OPPs, it is necessary to develop a simple, green, high-accuracy and high-reliability analysis method.

Disclosure of Invention

The invention aims to provide an electrode modified by a gadolinium oxide nano hollow sphere, a preparation method thereof, an electrochemical sensor and application thereof. Moreover, the preparation method of the gadolinium oxide nano hollow sphere modified electrode is simple and easy to control, and has high popularization and application values. The invention can also provide experimental basis for the research and development of the detection technology of methyl parathion and provide new thinking and new technology for the detection of pesticide residues in food.

In order to achieve the purpose, the invention provides a preparation method of an electrode modified by gadolinium oxide nano hollow spheres, which comprises the following steps: (1) adding polydopamine beads into an aqueous solution containing gadolinium salt and urea for mixing and contacting to obtain an intermediate of the polydopamine beads wrapped by basic gadolinium carbonate; (2) calcining the intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate at high temperature in air to obtain a gadolinium oxide hollow sphere; (3) and (3) dropwise coating the dispersion liquid containing the gadolinium oxide hollow spheres on the surface of the glassy carbon electrode, and then dropwise coating a Nafion diluent on the surface of the glassy carbon electrode to obtain the gadolinium oxide nano hollow sphere modified electrode.

The invention also provides an electrode modified by the gadolinium oxide nano hollow sphere prepared by the preparation method.

The invention also provides an electrochemical sensor, which comprises a working electrode, an auxiliary electrode, a reference electrode and electrolyte; wherein, the working electrode is the electrode modified by the gadolinium oxide nano hollow sphere.

Moreover, the invention also provides an application of the electrode modified by the gadolinium oxide nano hollow sphere and the electrochemical sensor in detecting methyl parathion.

In the technical scheme, the polydopamine bead is used as a template, an intermediate of the polydopamine wrapped by gadolinium hydroxide is obtained by using a urea-assisted homogeneous precipitation method, the intermediate is calcined in the air, the polydopamine bead is removed to obtain a gadolinium oxide nano hollow sphere, and the gadolinium oxide hollow sphere is modified on the surface of a glassy carbon electrode to obtain the gadolinium oxide nano hollow sphere modified electrode. The gadolinium oxide nanometer hollow sphere modified electrode can be used for detecting methyl parathion, is low in detection limit, good in linearity, high in stability and reproducibility and strong in anti-interference capability. Moreover, the preparation method of the gadolinium oxide nano hollow sphere modified electrode is simple and easy to control, and has high popularization and application values. The invention can also provide experimental basis for the research and development of the detection technology of methyl parathion and provide new thinking and new technology for the detection of pesticide residues in food.

Therefore, we speculate that: the polydopamine surface contains rich amino and phenolic hydroxyl groups, has chelating capacity for metal ions and strong adhesion, metal salt solution is easily adsorbed on the surface of the polydopamine surface, an intermediate of basic gadolinium carbonate coated polydopamine beads is obtained by using a urea-assisted homogeneous precipitation method, the intermediate is calcined in the air, and the polydopamine beads are removed to obtain the gadolinium oxide hollow nanospheres with a hollow structure with complete appearance and uniform size. Compared with the prior art, the modified electrode provided by the invention overcomes the problem of poor stability and repeatability of a general electrochemical sensor, has stable property and is simple to manufacture, and in the aspect of material selection, because the gadolinium rare earth element has a special 4f electronic layer, the gadolinium oxide hollow nanosphere has a large specific surface area and good electrocatalytic performance, and the rare earth oxide hollow nanosphere material has more excellent sound, light, electricity, magnetism, catalysis and other performances by combining the structural characteristics of the inorganic hollow nanosphere and the nano effect of the nano material, so that the sensitivity of parathion-methyl detection is improved.

The gadolinium oxide hollow nanospheres with uniform size and a hollow structure are synthesized by using carbon Spheres (PDAs) as templates, the gadolinium oxide hollow nanospheres have large specific surface area and good electrocatalytic performance, methyl parathion is detected by using modified electrodes of the gadolinium oxide hollow nanospheres, the gadolinium oxide hollow nanospheres are researched by cyclic voltammetry and differential pulse method, the linear range of the electrochemical sensor for detecting the methyl parathion is 0.05-100 mu M, and the linear equation is Y-0.1187 + 0.1834X (R is R²0.993), the lowest detection limit is 0.03 mu M, and the recovery rate of the methyl parathion is 95.5 to 106 percent in the recovery experiment of Chinese cabbage, tap water and paddy field water. The electrochemical sensor prepared by the research shows good stability and repeatability, the detection process is simple to operate, the cost is low, the detection range is wide, the detection limit is low, and the on-site rapid detection of the organophosphorus pesticide in the edible agricultural products is expected to be realized.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a transmission electron microscope characterization and a scanning electron microscope characterization for example 1;

FIG. 2 is a graph showing the characterization of X-ray photoelectron spectroscopy in example 1;

FIG. 3 is a graph representing an energy scattering X-ray analysis in example 1;

FIG. 4 is a powder X-ray diffraction pattern of example 1;

FIG. 5 is a graph showing the relationship between current and concentration obtained when methyl parathion in example 1 is applied;

FIG. 6 is a graph of the current versus concentration obtained when methyl parathion of example 1 was used;

FIG. 7 is a stability profile of the electrochemical sensor in detection example 1;

FIG. 8 is a characteristic view showing reproducibility of an electrochemical sensor in detection example 2;

fig. 9 is a graph showing the interference resistance characteristics of the electrochemical sensor of detection example 3.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a preparation method of an electrode modified by gadolinium oxide nano hollow spheres, which comprises the following steps: (1) adding polydopamine beads into an aqueous solution containing gadolinium salt and urea for mixing and contacting to obtain an intermediate of the polydopamine beads wrapped by basic gadolinium carbonate; (2) calcining the intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate at high temperature in air to obtain a gadolinium oxide hollow sphere; (3) and (3) dropwise coating the dispersion liquid containing the gadolinium oxide hollow spheres on the surface of the glassy carbon electrode, and then dropwise coating a Nafion diluent on the surface of the glassy carbon electrode to obtain the gadolinium oxide nano hollow sphere modified electrode.

Carbon Spheres (PDAs) are used as moldsThe plates are synthesized into gadolinium oxide nano hollow spheres with uniform size and a hollow structure, the gadolinium oxide nano hollow spheres have large specific surface area and good electrocatalysis performance, the modified electrodes are used for detecting methyl parathion, cyclic voltammetry and differential pulse method are used for researching, the linear range of the electrochemical sensor for detecting the methyl parathion is 0.05-100 mu M, and the linear equation is Y-0.1187 + 0.1834X (R is R)²0.993), the lowest detection limit is 0.03 mu M, and the recovery rate of the methyl parathion is 95.5 to 106 percent in the recovery experiment of Chinese cabbage, tap water and paddy field water. The electrochemical sensor prepared by the research shows good stability and repeatability, the detection process is simple to operate, the cost is low, the detection range is wide, the detection limit is low, and the on-site rapid detection of the organophosphorus pesticide in the edible agricultural products is expected to be realized.

In the above technical solution, the polydopamine beads can be prepared by using the commercial products or the prior art, and in the following examples, the polydopamine beads used in the present invention are prepared by the following method: polydopamine beads (PDAs) are synthesized in a water-alcohol mixed solvent, and 28mL of CH is added into 112mL of ultrapure water₃And OH, stirring and mixing. To the mixed solution of methanol/ultrapure water, ammonia (NH) was added in a volume of 0.75mL at room temperature₄OH, 28-30%), stirring and mixing for 30min, and adding 0.5g dopamine hydrochloride into the mixed solution. The solution gradually turned yellow-brown and finally black-brown and was stirred at room temperature for 30 h. And after the reaction is finished, centrifuging, respectively washing with ethanol and water, and drying the obtained product in a vacuum drying oven at 60 ℃ overnight to obtain the polydopamine beads.

In the above technical solution, the addition amount ratio of the polydopamine bead, the gadolinium salt, and the urea in step (1) can be selected in a wide range, and in order that the electrode modified by the gadolinium oxide nano hollow sphere can be used for detecting methyl parathion, and has low detection limit, good linearity, high stability and reproducibility, and strong anti-interference capability, preferably, the addition amount ratio of the polydopamine bead, the gadolinium salt, and the urea in step (1) is 0.2: 5-7: 0.5-2.

In order to detect methyl parathion, the gadolinium oxide nano hollow sphere modified electrode has low detection limit, good linearity, higher stability and reproducibility, and strong anti-interference capability, preferably comprises: mixing and contacting at 70-85 deg.C for 0.8-1.2 hr, and further mixing and contacting at 10-30 deg.C for 15-25 hr.

Furthermore, in order that the electrode modified by the gadolinium oxide nano hollow sphere can be used for detecting methyl parathion, has low detection limit, good linearity, higher stability and reproducibility and strong anti-interference capability, the method preferably further comprises the step of dispersing the polydopamine spheres in water and/or ethanol before mixing and contacting, and then adding the polydopamine spheres into an aqueous solution containing gadolinium salt and urea.

In the above technical solution, the high-temperature calcination conditions in step (2) may be selected in a wide range, so that the gadolinium oxide nano hollow sphere modified electrode can be used for detecting methyl parathion, and has a low detection limit, good linearity, high stability and reproducibility, and strong anti-interference capability, preferably, the high-temperature calcination conditions in step (2) include: calcining at 400-600 deg.C for 2-4 h.

Furthermore, in order that the electrode modified by the gadolinium oxide nano hollow sphere can be used for detecting methyl parathion, and has the advantages of low detection limit, good linearity, higher stability and reproducibility, and strong anti-interference capability, preferably, the calcining process comprises the following steps: firstly heating from room temperature to 380-420 ℃, and maintaining at 380-420 ℃ for 0.8-1.2 h; then the temperature is increased to 530 ℃ and 580 ℃, the temperature is reduced to 10-30 ℃ after being maintained at 530 ℃ and 580 ℃ for 1.5-2.5h, the temperature rising rate is 0.8-1.5 min/DEG C, and the temperature reduction rate is 4-6 min/DEG C.

In the above technical scheme, the mass ratio of the gadolinium oxide hollow spheres to water in the dispersion liquid of step (3) can be selected in a wide range, and in order that the gadolinium oxide nano hollow sphere modified electrode can be used for detection of methyl parathion, and has the advantages of low detection limit, good linearity, high stability and reproducibility, and strong anti-interference capability, preferably, the mass ratio of the gadolinium oxide hollow spheres to water in the dispersion liquid of step (3) is 4-10: 1000.

The mass fraction of the Nafion diluent can be selected in a wide range, so that the electrode modified by the gadolinium oxide nano hollow sphere can be used for detecting methyl parathion, the detection limit is low, the linearity is good, the stability and the repeatability are high, the anti-interference capability is strong, and preferably, the mass fraction of the Nafion diluent is 4-8%.

In the technical scheme, the gadolinium salt can be selected in various ways, the gadolinium salt can be realized as long as the gadolinium salt is soluble in water, and in order to obtain the gadolinium oxide nano hollow sphere modified electrode which can be used for detecting methyl parathion, the gadolinium oxide nano hollow sphere modified electrode is low in detection limit, good in linearity, high in stability and reproducibility, and strong in anti-interference capability, preferably, the gadolinium salt is one or more of gadolinium nitrate hexahydrate, gadolinium acetate and gadolinium carbonate.

In the technical scheme, the method further comprises the step of pretreating the glassy carbon electrode before the glassy carbon electrode is modified by the gadolinium oxide hollow spheres. The pretreatment mode has various options, and the invention can be realized by random combination and application of the pretreatment mode by persons skilled in the art, and the details are not repeated herein. In the following examples, the step of pretreating the glassy carbon electrode comprises: polishing the surface of the bare glassy carbon electrode by using the alumina powder; ultrasonically cleaning the electrode by respectively using ultrapure water and ethanol; and (5) washing the surface of the bare glassy carbon electrode by using ultrapure water, and airing at room temperature for later use.

The auxiliary electrode, the reference electrode and the electrolyte can be conventional in the art. For example, an electrochemical sensor for detecting methyl parathion can be prepared by using a platinum wire electrode as an auxiliary electrode, a calomel electrode as a reference electrode, and a 0.05mol/L PBS (pH 7) solution as an electrolyte, and the like, thereby achieving the effect of the invention.

Moreover, the invention also provides an application of the electrode modified by the gadolinium oxide nano hollow sphere in the detection of methyl parathion.

Taking a modified electrode modified by the gadolinium oxide nano hollow sphere as a working electrode, selecting a platinum wire electrode as an auxiliary electrode, a calomel electrode as a reference electrode and the modified electrode as the working electrode, adopting a DPV method in a three-electrode testing system,

The present invention will be described in detail below by way of examples. In the following examples, electrochemical detection was performed on a chemical workstation of the Shanghai Chenghua apparatus, model CHI440 a; x-ray photoelectron spectroscopy characterization (XPS) obtained by Al Ka radiation from Thermo Fisher Scientific, USA, thermocouple ESCALAB250XI spectrometer; the element content analysis is obtained by an energy scattering X-ray (EDX) spectrometer, and the transmission electron microscope characterization is carried out on a transmission electron microscope with the model number of 120KV HT7700 of Hitachi company in Japan; the scanning electron microscope is characterized by using a scanning electron microscope of a Regulus-8100 model of Hitachi corporation in Japan; powder X-ray diffraction (XRD) data were obtained by D8ADVANCEBRUKER, Germany, at diffraction angles of 10-100 deg., and at a sweep rate of 0.1S per degree.

The purity of the dopamine hydrochloride is more than 98%; the purity of the gadolinium nitrate hexahydrate is 99 percent; urea purity > 99.5%; the methyl parathion is purchased from Hefebailewei chemical technology Co., Ltd, and the CAS number is 298-00-0; the methanol and the ammonia water are analytically pure and are purchased from Shanghai Lingfeng Chemicals Co.

Preparation example

Polydopamine beads (PDAs) are synthesized in a water-alcohol mixed solvent, and 28mL of CH is added into 112mL of ultrapure water₃And OH, stirring and mixing. To the mixed solution of methanol/ultrapure water, 0.75mL of aqueous ammonia (NH4OH, 28 to 30%) was added at room temperature, and after stirring and mixing for 30min, 0.5g of dopamine hydrochloride was added to the mixed solution. The solution gradually turned yellow-brown and finally black-brown and was stirred at room temperature for 30 h. And after the reaction is finished, centrifuging, respectively washing with ethanol and water, and drying the obtained product in a vacuum drying oven at 60 ℃ overnight to obtain the polydopamine beads.

The appearance characterization comprises a transmission characterization and a scanning characterization, and the specific result is shown as a and b in figure 1; as can be seen from a and b in FIG. 1, the polydopamine sphere is solid and has a smooth surface, and the diameter of the sphere is 600 nm.

Example 1

Dissolving 0.2g of polydopamine in the preparation example by using 2mL of ultrapure water and 3mL of ethanol, performing ultrasonic treatment for 25min for later use, adding 5mL of 0.5 hexahydrate gadolinium nitrate solution and 6g of urea into 60mL of ultrapure water, stirring and mixing, adding ultrasonic polydopamine beads, performing water bath for 1h at the temperature of 80 ℃, stirring and reacting for 20h at normal temperature after the water bath is finished, centrifuging after the reaction is finished, respectively washing by using ethanol and water, and drying the obtained product at 60 ℃ overnight in a vacuum drying oven to obtain an intermediate of the basic gadolinium carbonate coated polydopamine beads.

Calcining the intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate in the air at a high temperature, raising the temperature from 20 ℃ to 400 ℃, and maintaining the temperature at 400 ℃ for 1 h. Then heating to 550 ℃, maintaining at 550 ℃ for 2h, and then cooling to 20 ℃, wherein the heating rate is 1 min/DEG C, the cooling rate is 5 min/DEG C, and the gadolinium oxide hollow sphere is obtained after calcination;

polishing the surface of the bare glassy carbon electrode by using the alumina powder; ultrasonically cleaning the electrode by respectively using ultrapure water and ethanol; washing the surface of the bare glassy carbon electrode by using ultrapure water, and airing at room temperature for later use; and (3) mu.L of gadolinium oxide dispersion liquid (5mg/mL) is dripped on the surface of the air-dried bare glass carbon by using a liquid transfer gun, and then 1 mu.L of LNafion diluent (5 wt%) is dripped to obtain the gadolinium oxide nano hollow sphere modified electrode.

The shape representation of the intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate comprises transmission representation and scanning representation, and the results are respectively shown as c and d in fig. 1; as can be seen from c and d in fig. 1, the surface of the intermediate becomes rough due to the covering of the surface of the polydopamine sphere with gadolinium hydroxycarbonate, while maintaining the spherical appearance and monodispersity consistent with that of the template PDA.

The shape characterization of the gadolinium oxide hollow sphere comprises a transmission characterization and a scanning characterization, and the transmission electron microscope characterization is carried out on a transmission electron microscope with the model number of 120KV HT7700 of Hitachi, Japan; scanning electron microscopy characterization was performed on a scanning electron microscope, model Regulus-8100, Hitachi, Japan, and the results are shown in FIG. 1, e and f, respectively. As can be seen from e and f in fig. 1, the appearance of the spheres remains intact and the diameters of the spheres become smaller as compared to the intermediate due to shrinkage during calcination.

The X-ray photoelectron spectroscopy characterization (XPS) was obtained by Al Ka radiation from Thermo Fisher Scientific, USA, and thermocouple ESCALB 250XI spectrometer; the element content analysis was obtained by an energy scattering X-ray (EDX) spectrometer; powder X-ray diffraction (XRD) data were obtained by D8ADVANCEBRUKER, Germany; the specific results are shown in fig. 2, fig. 3, fig. 4, and the electron binding energy spectrum generated by the electron transition of Gd, O, and C elements in fig. 2, wherein Gd content is 82.34% and O content is 13.89% in fig. 3. The diffraction peak shape in FIG. 4 is sharp and has no impurity peak, which indicates that the purity of the sample is high, and the crystal face corresponding to the peak position can completely match Gd₂O₃(PDF #43-1014) are matched. The above-mentioned morphological and elemental analysis proves that Gd is successfully prepared by the invention₂O₃And (3) a hollow nano-sphere material.

In the same way, for the embodiment

Example 2

(1) Firstly dispersing polydopamine beads in water and/or ethanol, then adding an aqueous solution containing gadolinium salt and urea, mixing and contacting for 1.2h at 70 ℃, and then continuously mixing and contacting for 25h at 10 ℃, wherein the addition mass ratio of the polydopamine beads to the gadolinium salt to the urea is 0.2: 0.5: 5, obtaining an intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate;

(2) calcining the intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate in the air at a high temperature, heating the intermediate to 380 ℃ from room temperature, and maintaining the intermediate at 380 ℃ for 1.2 h; then heating to 530 ℃, maintaining at 530 ℃ for 2.5h, and then cooling to room temperature, wherein the heating rate is 0.8 min/DEG C, and the cooling rate is 4 min/DEG C, so as to obtain a gadolinium oxide hollow sphere;

(3) and (3) dropwise coating 3 mu L of dispersion liquid containing the gadolinium oxide hollow spheres (the mass ratio of the gadolinium oxide hollow spheres to water in the dispersion liquid is 4:1000) on the surface of the glassy carbon electrode, and then dropwise coating 1 mu L of Nafion diluent (the mass fraction is 4%) on the surface of the glassy carbon electrode to obtain the gadolinium oxide nano hollow sphere modified electrode.

Example 3

(1) Firstly dispersing polydopamine beads in water and/or ethanol, then adding an aqueous solution containing gadolinium salt and urea, mixing and contacting for 0.8h at 85 ℃, and then continuously mixing and contacting for 15-25h at 30 ℃, wherein the addition ratio of the polydopamine beads to the gadolinium salt to the urea is 0.2: 2: 7, obtaining an intermediate of polydopamine beads wrapped by basic gadolinium carbonate;

(2) calcining the intermediate of the polydopamine bead wrapped by the basic gadolinium carbonate in the air at a high temperature, heating the intermediate to 420 ℃ from room temperature, and maintaining the intermediate at 420 ℃ for 0.8 h; then heating to 580 ℃, maintaining the temperature at 580 ℃ for 1.5, and then cooling to 10-30 ℃, wherein the heating rate is 1.5 min/DEG C, and the cooling rate is 6 min/DEG C, so as to obtain the gadolinium oxide hollow sphere;

(3) and (3) dripping 3 mu L of dispersion liquid containing the gadolinium oxide hollow spheres (the mass ratio of the gadolinium oxide hollow spheres to water in the dispersion liquid is 10:1000) on the surface of the glassy carbon electrode, and dripping 1 mu L of Nafion diluent (the mass fraction is 8%) on the surface of the glassy carbon electrode to obtain the gadolinium oxide nano hollow sphere modified electrode.

In the same way, the same detection and characterization are carried out on the gadolinium oxide hollow spheres in the

embodiments

2 and 3, the result is similar to that in the embodiment 1, and the Gd is prepared₂O₃And (3) a hollow nano-sphere material.

Application example 1

Constructing an electrochemical sensor: 0.05mol/L PBS solution is used as electrolyte, a modified electrode is used as a working electrode, a platinum wire electrode is selected as an auxiliary electrode, a calomel electrode is used as a reference electrode, and the modified electrode is used as the working electrode.

A DPV method is adopted in a three-electrode test system, firstly nitrogen is introduced into the electrolyte for 10-15min, then DPV test is carried out, the enrichment time in each test is 30s, the enrichment potential is-0.6V, and the relation between the peak current and the concentration of methyl parathion is measured. Referring to FIGS. 5, 6, the abscissa E/V of FIG. 5 represents voltage in volts V; accident Current (μ A) represents Current in μ A. FIG. 6 shows the Concentration of methyl parathion in μ M on the abscissa and the Current (μ A) on the ordinate. The unit is μ A. According to FIG. 6, the peak current and the concentration of methyl parathion are in a linear relationship, and a working curve is drawn; the measurement result shows that the concentration of the methyl parathion is in a linear relation within the range of 0.05-100 mu M, the linear coefficient is 0.993, and the detection limit is 0.03 mu M.

Detection example 1

The electrochemical sensor is stored at 4 ℃, the prepared modified electrode is used as a working electrode, a platinum wire electrode is selected as an auxiliary electrode, a calomel electrode is used as a reference electrode, 0.05mol/L PBS (pH 7) solution is used as electrolyte, a three-electrode test system is firstly placed into the electrolyte, nitrogen is introduced for 10-15min, then DPV test is carried out, the DPV selects an enrichment potential of-0.6V, the enrichment time is 30s, the concentration of methyl parathion is 100 mu M, response current is detected at three days intervals, response current is detected at six days intervals, and after the electrochemical sensor is stored for 15 days, the response current is maintained at 94.9% of the initial current, which indicates that the electrochemical sensor has better stability. The specific result is shown in fig. 7, and the relation between the peak current and the time can be seen, which indicates that the electrochemical sensor has better stability.

Detection example 2

The test of the reproducibility of the electrochemical sensor of the invention takes 5 modified electrodes prepared under the same condition to measure the response current of 100 mu M methyl parathion under the same condition, a DPV method is adopted in the process, the enrichment potential selected by the DPV is-0.6V, the enrichment time is 30s, and the response currents measured by the 5 electrochemical sensors are transversely compared to obtain that the relative standard deviation is 3.9 percent. The specific result is shown in fig. 8, and the response of the peak current measured by the modified electrode under 5 parallel conditions can be seen, which proves that the sensor has good reproducibility.

Detection example 3

The invention discloses a test of the anti-interference capability of an electrochemical sensor, which is used for detecting a target object, namely Methyl Parathion (MP), and interfering substances, such as Ascorbic Acid (AA), Hydroquinone (HQ), D-glucose (Glu), M-nitrophenol (M-NP), imidacloprid (IMI) and pyrazosulfuron-ethyl (PSE). The molecular structural formulas of the detection target substance and the interference substance are as follows.

Adopting DPV method to measure, using the prepared modified electrode as a working electrode, selecting a platinum wire electrode as an auxiliary electrode, using a calomel electrode as a reference electrode, 0.05mol/L PBS (pH 7) solution is taken as electrolyte, the three-electrode test system is firstly put into the electrolyte, nitrogen is introduced for 10-15min, the enrichment potential selected by DPV is-0.6V, the enrichment time is 30s, the concentration of each substance is 100 mu M, the response current of the interfering substance is compared with the response current of methyl parathion, wherein the interference signal of Ascorbic Acid (AA) is 4.3%, the interference signal of Hydroquinone (HQ) is 4.9%, the interference signal of D-glucose (Glu) is 5.2%, the interference signal of M-nitrophenol (M-NP) is 4.8%, the interference signal of imidacloprid (IMI) is-2.4%, and the interference signal of pyrazosulfuron-ethyl is 9.4%. The specific result is shown in figure 9, and the electrochemical sensor has better anti-interference performance.

Application example 2

According to the test of the practical application of the electrochemical sensor, the Chinese cabbage is selected as a practical sample, the extract of the Chinese cabbage, tap water and paddy field water are selected as the practical sample; the standard concentration of methyl parathion is 1 muM, 3 muM and 5 muM respectively, and the results are shown in Table 1. The recovery rate is 95.5-106%. Indicating that the practicability is better.

TABLE 1

The gadolinium oxide hollow spheres in the

embodiments

2 and 3 are detected and applied in the same way, and the obtained detection result is similar to that in the embodiment 1, so that the preparation of the gadolinium oxide nano hollow sphere modified electrode and the electrochemical sensor is proved.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. a preparation method of an electrode modified by gadolinium oxide nano hollow spheres, is characterized in that, comprises the following steps:

(1) adding polydopamine pellets to an aqueous solution containing gadolinium salt and urea for mixing and contacting to obtain an intermediate of basic gadolinium carbonate-coated polydopamine pellets;

(2) calcining the intermediate of basic gadolinium carbonate-wrapped polydopamine pellets at high temperature in air to obtain gadolinium oxide hollow spheres;

(3) Coating the dispersed droplet containing gadolinium oxide hollow spheres on the surface of the glassy carbon electrode, and then dripping Nafion diluent on the surface of the glassy carbon electrode to obtain an electrode modified by gadolinium oxide nano hollow spheres.

2. The preparation method according to claim 1, wherein the ratio of the added mass of polydopamine pellets, gadolinium salt and urea in step (1) is 0.2:0.5-2:5-7.

3 . The preparation method according to claim 2 , wherein the process of mixing and contacting in step (1) comprises: firstly mixing and contacting at 70-85° C. for 0.8-1.2 hours, and then continuing to mix and contact at 10-30° C. for 15-25 hours. 4 . .

4. The preparation method according to claim 3, wherein, before mixing and contacting, the polydopamine pellets are dispersed in water and/or ethanol, and then added to the aqueous solution containing gadolinium salt and urea. step.

5 . The preparation method according to claim 1 , wherein the conditions for high temperature calcination in step (2) include: calcination at 400° C.-600° C. for 2-4 hours. 6 .

6. The preparation method according to claim 5, wherein the calcination process comprises: firstly heating from room temperature to 380-420°C, maintaining at 380-420°C for 0.8-1.2h; then heating to 530-580°C, at 530-420°C After maintaining at 580°C for 1.5-2.5h, the temperature is lowered to 10-30°C, the heating rate is 0.8-1.5min/°C, and the cooling rate is 4-6min/°C.

7. The preparation method according to any one of claims 1-4, wherein the mass ratio of gadolinium oxide hollow spheres to water in the dispersion in step (3) is 4-10:1000.

8. The preparation method according to any one of claims 1-4, wherein the mass fraction of the Nafion diluent is 4-8%.

9. The preparation method according to any one of claims 1-4, wherein the gadolinium salt is one or more of gadolinium nitrate hexahydrate, gadolinium acetate and gadolinium carbonate.

10. An electrode modified with gadolinium oxide nano hollow spheres prepared by the preparation method according to any one of claims 1-9.

11 . An electrochemical sensor, characterized in that it comprises a working electrode, an auxiliary electrode, a reference electrode and an electrolyte; wherein the working electrode is an electrode modified by the gadolinium oxide nano hollow spheres according to claim 10 .

12. The application of the electrochemical sensor of claim 11 in detecting methyl parathion.