A magnetic functional material of carbon nanotubes loaded with Co nanoparticles, its preparation method and application

Abstract

The application discloses a kind of Co nanoparticle loaded carbon nanotube magnetic functional materials (Co@CNTs) preparation. Due to the synergistic effect of Co nanoparticle and carbon tube, the material shows excellent electrocatalytic, conductivity, fast electron transfer ability. Combined with the design of magnetic base and screen printed electrode (SPE), a kind of renewable magnetic screen printed electrode is developed. Among them, the presence of Co@CNTs greatly improves the electron transfer dynamics of hydrazine hydrate and tartrazine on the surface of SPE. The linear range of Co@CNTs / SPCE for hydrazine hydrate and tartrazine detection is 0.1~50.0 mM and 0.04~30.0 mM, and the detection limit is 50 nM and 12 nM respectively. Since Co@CNTs is attached to the surface of SPE by magnet control, and is easy to separate from the electrode surface by magnet, the sensor structure is simple, renewable and low cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical analysis, and particularly provides a Co nanoparticle-loaded carbon nanotube magnetic functional material and a preparation method and application thereof. BACKGROUND

[0002] Magnetic functional nanomaterials have been widely used as catalysts or adsorbents due to their easy operation and simple separation. Under the action of an external magnetic field, their controllable spatial distribution can make them applied to interface-related fields. And through magnetic separation, the magnetic materials can be quickly and effectively recovered and regenerated, which will potentially reduce capital investment. In addition, through size effect and chemical composition, some controllable magnetic nanomaterials have been developed. Iron, cobalt, nickel and other metals are used as the main magnetic source due to their high saturation magnetization. However, the chemical stability of pure metal nanoparticles is poor because of their weak oxidation resistance. In order to improve the stability of magnetic nanomaterials and obtain magnetic nanomaterials with specific functions, researchers use the method of combining magnetic elements with other substrates. For example: a magnetic nanofiber loaded with iron oxide is synthesized for the manufacture of a morphine electrochemical sensor; a magnetic cellulose-chitosan hydrogel combined with Fe3O4 is prepared for the removal of heavy metal ions; a separable and recyclable magnetic carbon nanotube is prepared, and Ni nanoparticles are coated thereon for Hg 2+ detection; a magnetic Ni@NCNT is synthesized for the removal of pollutants by persulfate activation, and the Ni@NCNT still has strong magnetism and stability after acid washing.

[0003] A screen-printed electrode (SPE) is a substitute for traditional electrodes, which generally includes a substrate on which an external insulating layer and electrode leads are printed, and three electrodes are printed on the substrate, respectively, a working electrode (WE), a reference electrode (RE) and an auxiliary electrode (AE), each electrode is connected to the corresponding lead to form a classic electrochemical three-electrode system. It has the following characteristics: small size, powerful, can realize on-site and real-time analysis; multifunctional, customizable, can meet various needs; high repeatability; low cost, maintenance-free. Because it has characteristics and advantages that traditional electrodes cannot replace, it has applications in the environment, clinical or agricultural food fields. However, the screen-printed electrodes used now are disposable electrodes, and for some types that use printed gold paste as the working electrode, the use cost is relatively high. Therefore, we propose a preparation method of a regenerable magnetic screen-printed electrode by combining the advantages of magnetic materials. The magnetic functional nanomaterials are controlled to adhere to the surface of the screen-printed electrode by designing a magnetic base, and the magnetic functional materials are separated from the surface of the electrode by a magnet to achieve the purpose of regenerating the electrode surface. SUMMARY

[0004] The application aims to provide a preparation method and application of a carbon nanotube magnetic functional material loaded with Co nanoparticles.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the application comprises: a preparation method of a carbon nanotube magnetic functional material (Co@CNTs) loaded with Co nanoparticles, wherein a proper amount of dried and dehydrated cobalt metal salt, starch and dicyandiamide are mixed, the mixture is transferred into an alumina crucible after ball milling, and the mixture is heated in a tube furnace through programmed temperature rising, double-stage temperature control pyrolysis, and the black product is collected after cooling.

[0006] Preferably, the mass ratio of the dicyandiamide and the starch is 3:1-20:1; the step heating temperature rising rate is 2-4°C·min-1; the double-stage pyrolysis control temperatures are 850-900 K and 1050-1100 K respectively, and the control temperature time is 2-8 h and 1-4 h respectively; and the tube furnace is protected by N2 or Ar gas.

[0007] Preferably, the mass ratio of the dicyandiamide and the metal Co salt is 2:1-20:1.

[0008] The carbon nanotube magnetic functional material (Co@CNTs) loaded with Co nanoparticles prepared according to the method.

[0009] The application of the carbon nanotube magnetic functional material (Co@CNTs) loaded with Co nanoparticles prepared according to the method in preparing a renewable magnetic screen printing electrode.

[0010] The preparation method of the renewable magnetic screen printing electrode comprises the following steps:

[0011] (1) designing a magnetic base: containing a basic base, a hard electrode clamping groove, a magnet with a proper size, an electrode water platform, and a fixing screw;

[0012] (2) inserting the screen printing electrode into the magnetic base, activating, dispersing the Co@CNTs in a proper solvent, dropping the Co@CNTs dispersion on the surface of the working electrode, and then absorbing the solvent with filter paper and cleaning. In order to regenerate the electrode surface, the electrode is taken off from the magnetic base and the Co@CNTs is absorbed by the magnet.

[0013] Preferably, the materials of the parts in step (1) are all insulating materials, the size range of the basic base is 6-15 cm in length and 2-6 cm in width, and the magnet is fixed on the base.

[0014] Preferably, the size of the hard clamping groove in step (1) matches the size of the screen printing electrode; the hard electrode clamping groove fixes the screen printing electrode, and the screw fixes the electrode clamping groove; the size of the magnet is consistent with the size of the working electrode of the screen printing electrode, and the relative horizontal position overlaps; and the electrode water platform stabilizes the electrode adapter.

[0015] Preferably, the mass concentration of the Co@CNTs dispersion liquid in step (2) is 0.2-4.0 mg / mL; the method for activating the screen-printed electrode is as follows: in 0.1 mol / L H2SO4, cyclic voltammetry is used to cyclically scan at a certain scan rate in the range of-0.6 V to +1.2 V for 4-10 cycles, then washing and drying under N2.

[0016] According to the method, the renewable magnetic screen-printed electrode prepared from the magnetic functional material and the application thereof are provided.

[0017] In the present application, the carbon nanotubes loaded with Co nanoparticles are prepared by high-temperature pyrolysis, and the renewable magnetic screen-printed electrode is prepared by modifying the carbon nanotubes loaded with Co nanoparticles on the surface of the screen-printed electrode by drop coating. The oxidation peak current of the electrode has a linear correlation with the content of hydrazine hydrate and tartrazine. The carbon nanotubes loaded with Co nanoparticles (Co@CNTs) have a large specific surface area and excellent electron transfer rate. Due to the loading of Co metal nanoparticles, the electrocatalytic performance is greatly improved through the synergistic effect with the carbon nanotubes. The renewable magnetic screen-printed electrode prepared from the material can rapidly determine the content of hydrazine hydrate and tartrazine, and has a low detection limit. The magnetic functional nanomaterial can be controlled to be attached to the surface of the screen-printed electrode by a magnet, and can also be completely separated from the surface of the electrode by a magnet, so that the electrode is regenerated and the cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The scanning electron microscope (SEM) image (A) and the transmission electron microscope (TEM) image (B) of the carbon nanotubes loaded with Co nanoparticles prepared in Example 1 are shown.

[0019] Figure 2 The dispersion diagrams of the carbon nanotubes loaded with Co nanoparticles prepared in Example 1 in the presence / absence of a magnetic field are shown.

[0020] Figure 3 The schematic diagram of the magnetic base designed in Example 1 inserted into the screen-printed electrode is shown.

[0021] Figure 4 The cyclic voltammograms of the magnetic screen-printed electrode (Co@CNTs / SPE) prepared in Example 1 and the bare screen-printed electrode (SPE) for electrocatalytic oxidation of hydrazine hydrate (A) and tartrazine (B) are shown. DETAILED DESCRIPTION

[0022] The following is the preparation of the carbon nanotubes loaded with Co nanoparticles, the preparation of the renewable magnetic screen-printed electrode, and the detection of hydrazine hydrate and tartrazine. The following examples are intended to further illustrate the present application, but not to limit the present application. Example

[0023] (1) Preparation of Co nanoparticle loaded carbon nanotubes; 5.0 g of dicyandiamide, 0.5 g of starch, and 0.4 g of cobalt acetate were dry mixed and treated with a ball mill for 24 h. The solid powder was transferred into a tube furnace and heated at a rate of 4°C·min -1 to 873 K under N2 atmosphere, and kept at this temperature for 2 h. The temperature was then increased to 1073 K at a rate of 4°C·min -1 , and kept at this temperature for 2 h. After cooling, the black product was collected by grinding, and Co nanoparticle loaded carbon nanotubes (Co@CNTs) magnetic functional material was obtained.

[0024] (2) Design of magnetic base; the base has a size of 8 cm in length and 4 cm in width. A disc magnet with a diameter of 5 mm and a thickness of 2 mm is installed on the base. A hard screen-printed electrode slot is installed above the magnet, and the slot is fixed by screws. The inner cavity of the slot for fixing the screen-printed electrode has a size of 1´1.5 cm. The size of the base magnet is consistent with the size of the working electrode of the screen-printed electrode, and the relative positions can overlap. The screw-fixed electrode water platform stabilizes the electrode adapter, so that the screen-printed electrode can be stably kept in the horizontal direction.

[0025] (3) Construction of renewable magnetic screen-printed electrode (Co@CNTs / SPE): First, the printed electrode is inserted into the electrode slot of the designed magnetic base. 0.1 mol / L H2SO4 is added to the surface of the electrode, and the electrode is activated by cyclic voltammetry at a scan rate of 50 mV s -1 from -0.6 V to +1.2 V for 5 cycles. Then the electrode is washed with ethanol and dried on the surface under N2. Co@CNTs are dispersed in N,N-dimethylformamide. 6 mL of Co@CNTs dispersion (0.5 mg / mL) is added to the surface of the working electrode, and then the solvent is absorbed with filter paper and washed with water. In order to regenerate the electrode surface, the electrode is removed from the magnetic base, and the Co@CNTs on the surface of the electrode are absorbed by the magnet. After reactivating the electrode, the second material modification can be performed.

[0026] (4) Electrochemical determination of hydrazine hydrate: Co@CNTs / SPE constructed in step (3) is used as the electrical signal sensing device, and 0.1 mol / L phosphate buffer solution is used as the electrolyte with a pH value of 7.0. The test method is cyclic voltammetry. The standard concentration of the sample to be tested is added to the surface of the electrode, and the oxidation peak current value of hydrazine hydrate at different concentrations is recorded, and a standard curve of current-concentration is drawn. When testing the sample, the measured oxidation peak current value is compared with the standard curve to calculate the content of hydrazine hydrate in the sample to be tested.

[0027] (5) Characterization of the magnetic functional material obtained in this example and performance of the sensor: The magnetic functional material obtained in this example has a specific surface area of 1.5 m2 / g, a pore volume of 0.1 cm3 / g, and a pore size of 2.5 nm. The sensor has a detection limit of 0.1 mg / L, a linear range of 0.1-100 mg / L, and a response time of 5 s.Figure 1 It can be seen that the prepared material has a tubular structure loaded with metal nanoparticles, the nanoparticle size is about 10-80 nm, and the nanotube diameter is about 20-150 nm. Figure 2 It is shown that the prepared Co@CNTs has good magnetism. By Figure 3 , the designed magnetic base can stably fix the screen-printed electrode. By Figure 4 , it is found by comparison with the bare printed electrode (SPE) that the magnetic Co@CNTs / SPE greatly improves the oxidation peak of hydrazine hydrate, and the oxidation peak current is 6.7 times that of the former. Embodiment

[0028] (1) Preparation of carbon nanotubes loaded with Co nanoparticles, same as embodiment 1.

[0029] (2) Design of magnetic base; the base base size is 10 cm long and 3 cm wide; a disc magnet with a diameter of 5 mm and a thickness of 4 mm is installed on the base; an electrode clamping groove is glued and fixed above the magnet, and the cavity size of the clamping groove is 1´3 cm; the size of the base magnet is consistent with the size of the working electrode of the screen-printed electrode, and the relative position can overlap; the water platform stably fixes the electrode adapter, so that the screen-printed electrode can stably maintain the horizontal direction.

[0030] (3) Construction of renewable magnetic screen-printed electrode (Co@CNTs / SPE), same as embodiment 1.

[0031] (4) Electrochemical determination of tartrazine: Co@CNTs / SPE constructed in step (3) is used as an electrical signal sensing device, 0.1 mol / L phosphate buffer solution is used as an electrolyte, pH value is 6.5, test method is differential pulse voltammetry; the electrode surface is added with a standard concentration of tartrazine to be tested, the oxidation peak current value of tartrazine at different concentrations is recorded, and a standard curve of current-concentration is drawn. When testing the sample, the measured oxidation peak current value is compared with the standard curve to calculate the content of tartrazine in the sample to be tested.

[0032] (5) Sensing performance of the renewable Co@CNTs / SPE prepared in this embodiment: by Figure 4 It can be seen that, compared with the bare printed electrode (SPE), the magnetic Co@CNTs / SPE greatly improves the oxidation peak of tartrazine, and the peak current is 3.9 times that of the former. Embodiment

[0033] (1) Preparation of carbon nanotubes loaded with Co nanoparticles; 3.0 g of dicyandiamide, 0.8 g of starch and 0.5 g of hexammine cobalt trichloride are dried and mixed, and treated by ball milling for 15 h. The solid powder is transferred into a tube furnace, and the temperature is raised to 800°C at a rate of 2°C·min -1The temperature was increased to 823 K in stepwise increments, held at that temperature for 4 hours, and then increased at 2°C / min. -1 The temperature was increased to 1023 K at a certain rate, held at that temperature for 3 hours, cooled, ground thoroughly, and the black product was collected to obtain the magnetic functional material of carbon nanotubes (Co@CNTs) loaded with Co nanoparticles.

[0034] (2) The design of the magnetic base is the same as in Example 1.

[0035] (3) Construction of recyclable magnetic screen-printed electrodes (Co@CNTs / SPE): First, insert the printed electrode into the electrode slot of the designed magnetic base, and drop 0.1 mol / L H2SO4 onto the electrode surface, and then heat it at 20 mV s. -1 At a specific scan rate, cyclic voltammetry was used to scan the electrode 8 times within the range of -0.6 V to +1.2 V to activate it. The electrode was then rinsed with water and dried under N2. Co@CNTs were dispersed in ethanol. 10 mL of the Co@CNTs dispersion (3.0 mg / mL) was added dropwise to the working electrode surface, the ethanol was blotted dry with filter paper, and the electrode was rinsed with water. To regenerate the electrode surface, the electrode was removed from the magnetic base, and the Co@CNTs on the electrode surface were removed using a magnet. After electrode activation, secondary material modification can be performed.

[0036] (4) The electrochemical determination of hydrazine hydrate is the same as in Example 2.

Claims

1. A method for detecting hydrazine hydrate or tartrazine by using a magnetic functional material Co@CNTs prepared by Co-loaded nanoparticles carbon nanotubes, characterized in that, The method comprises the following steps: (1) preparing Co nanoparticle-loaded carbon nanotubes: a proper amount of dried and dehydrated cobalt metal salt, starch and dicyandiamide are mixed, the mixture is transferred into an alumina crucible after ball milling, and is heated in a tube furnace by programmed temperature rising, double-stage temperature control pyrolysis, and the black product is collected after cooling; (2) designing a magnetic base: containing a basic base, a hard electrode slot, a magnet of appropriate size, an electrode water platform and a fixing screw; (3) constructing a renewable magnetic screen-printed electrode: inserting the screen-printed electrode into the magnetic base, activating, and dispersing Co@CNTs in a suitable solvent; dropping Co@CNTs dispersion liquid on the surface of the working electrode, then absorbing the solvent with filter paper, and cleaning; in order to regenerate the electrode surface, the electrode is taken off from the magnetic base, and Co@CNTs is absorbed by the magnet; (4) electrochemical determination of hydrazine hydrate: taking the Co@CNTs / SPE constructed in step (3) as an electric signal sensing device, 0.1 mol / L phosphate buffer solution as an electrolyte, pH value is 7.0, and the test method is cyclic voltammetry; dropping the standard concentration of the to-be-tested liquid on the surface of the electrode, recording the oxidation peak current value of hydrazine hydrate at different concentrations, and drawing a standard curve of current-concentration; when detecting the sample, the measured oxidation peak current value is compared with the standard curve, and the content of hydrazine hydrate in the to-be-tested sample is calculated; or (4) electrochemical determination of tartrazine: taking the Co@CNTs / SPE constructed in step (3) as an electric signal sensing device, 0.1 mol / L phosphate buffer solution as an electrolyte, pH value is 6.5, and the test method is differential pulse voltammetry; dropping the standard concentration of tartrazine to-be-tested liquid on the surface of the electrode, recording the oxidation peak current value of tartrazine at different concentrations, and drawing a standard curve of current-concentration; when detecting the sample, the measured oxidation peak current value is compared with the standard curve, and the content of tartrazine in the to-be-tested sample is calculated.

2. The method of claim 1, wherein, The step (1) specifically comprises the following steps: (11) mixing a proper amount of dried and dehydrated cobalt metal salt, starch and dicyandiamide, wherein the mass ratio of dicyandiamide and starch is 3:1-20:1, and the mass ratio of dicyandiamide and metal Co salt is 2:1-20:1; (12) after ball milling, the mixture is transferred into an alumina crucible, heated in a tube furnace by programmed temperature rising under N2 or Ar gas protection, double-stage temperature control pyrolysis is carried out, the first stage is kept at 850-900 K for 2-8 hours, the second stage is kept at 1050-1100 K for 1-4 hours, and the temperature rising rate is 2-4 °C·min⁻¹; (13) collecting the black product after cooling, wherein the black product is a hollow carbon nanotube, and Co nanoparticles are located in the hollow cavity of the carbon nanotube.

3. The method of claim 1, wherein, The particle size of the Co nanoparticles is 10-80 nm, and the tube diameter of the carbon nanotube is 20-150 nm.

4. The method of claim 1, wherein, The cobalt metal salt is cobalt acetate or hexamine cobalt trichloride.

5. The method of claim 1, wherein, The materials of the parts in the step (2) are all insulating materials, the size range of the basic base is 6-15 cm in length and 2-6 cm in width, and the magnet is fixed on the base.

6. The method of claim 1, wherein, The size of the hard electrode slot in the step (2) is matched with the size of the screen-printed electrode; the hard electrode slot fixes the screen-printed electrode, and the screw fixes the electrode slot; the size of the magnet is consistent with the size of the working electrode of the screen-printed electrode, and the relative horizontal position is overlapped; and the electrode water platform stabilizes the electrode adapter.

7. The method of claim 1, wherein, The mass concentration of the Co@CNTs dispersion liquid in the step (3) is 0.2-4.0 mg / mL; and the method for activating the screen-printed electrode is: In 0.1 mol / L H2SO4, the cyclic voltammetry is used to cyclically scan 4-10 times at a certain scan rate in the range of-0.6 V to +1.2 V, then the screen-printed electrode is cleaned and dried under N2.

8. The method of claim 1, wherein, The solvent in the step (3) is N,N-dimethylformamide or ethanol.

Images