Composite carbon nanomaterial as well as preparation method and application thereof

Abstract

The invention relates to a composite carbon nanomaterial as well as a preparation method and application thereof, and belongs to the technical field of material preparation. The invention provides a preparation method of a composite carbon nanomaterial, which comprises the following steps: (1) stirring tetraethyl silicate in an alkaline solution, adding dopamine hydrochloride, continuously stirring, centrifuging, drying, calcining and etching to obtain N-doped hollow carbon spheres; and (2) uniformly mixing 2-methylimidazole and the N-doped hollow carbon spheres obtained in the step (1) in a solvent, carrying out rotary evaporation, adding a zinc source, continuously carrying out rotary evaporation, adding triethylamine, heating at a constant temperature, washing, centrifuging and drying to obtain the composite carbon nanomaterial. The prepared composite carbon material has high conductivity, high porosity, high specific surface area and excellent chemical stability, and when the composite carbon material is applied to detection of luteolin through an electrochemical method, the operation is simple, the cost is low, the reliability is high, the response speed is high, the detection cost is reduced to a great extent, and the detection efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and specifically relates to a composite carbon nanomaterial and a preparation method and application thereof. Background Art

[0002] Luteolin (3,4,5,7-tetrahydroxy-avone) is a natural flavonoid compound widely distributed in plants and fruits, such as celery, oranges, apples, etc. Luteolin is a natural medicine with many pharmacological activities, including: lowering uric acid, antibacterial, anti-tumor, anti-inflammatory, etc. In the food industry, it is regarded as an important food additive due to its good antioxidant and anti-inflammatory properties, used to improve the nutritional value of food and extend the shelf life.

[0003] Although luteolin is a natural medicine, excessive intake can cause symptoms such as dry mouth, stomach discomfort, dizziness, and nausea. Therefore, foods and medicines containing luteolin should be consumed in moderation, and follow the doctor's advice if necessary. In order to detect the content of luteolin in food, it is crucial to develop a fast, accurate, and convenient detection method. At present, the main methods for detecting luteolin are high-performance liquid chromatography, ultraviolet-visible spectrophotometry, capillary electrophoresis, etc.; although these methods are highly accurate, the disadvantages of expensive instruments, complex operations, and long detection time also make the detection of luteolin costly. In recent years, electrochemistry has entered everyone's field of vision due to its advantages such as simple equipment, simple operation, low cost, high reliability, and fast response speed, and is considered to be an ideal alternative method.

[0004] For electrochemical methods, suitable electrode materials play an important role and can greatly affect the detection effect. Therefore, it is urgent to develop a fast, accurate and convenient electrode material for the detection of luteolin. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art and to provide a composite carbon nanomaterial and a preparation method and application thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a composite carbon nanomaterial, comprising the following steps:

[0008] (1) stirring tetraethyl silicate in an alkaline solution, adding dopamine hydrochloride and continuing stirring, centrifuging, drying, calcining, and etching to obtain N-doped hollow carbon spheres;

[0009] (2) 2-methylimidazole and the N-doped hollow carbon spheres obtained in step (1) are uniformly mixed in a solvent, rotary evaporated, and then a zinc source is added, the rotary evaporated is continued, triethylamine is added, the mixture is heated at a constant temperature, washed, centrifuged, and dried to obtain the composite carbon nanomaterial.

[0010] The present invention develops a composite carbon nanomaterial based on N-doped hollow carbon sphere (HNC) and metal organic framework material (MOF, ZIF-8), which can be used for electrochemical sensing detection of luteolin. ZIF-8, as a Zn-based MOF material, is a highly ordered porous structure material with advantages such as high specific surface area and adjustable pore size. N-doped hollow carbon spheres form a special doped carbon material by introducing N atoms into carbon spheres, which has high conductivity and chemical stability and is an advanced nanomaterial. The present invention adopts a hard template method to use SiO2 as a template, and dopamine hydrochloride is coated on it. Carbon spheres are formed by high-temperature calcination and carbonization, and the template is etched to form hollow carbon spheres. Then, ZIF-8 is uniformly grown on the outside and inside of the N-doped hollow carbon spheres by an in-situ growth method, which can effectively avoid the agglomeration problem of ZIF-8 crystals. The obtained composite carbon material has high conductivity and excellent chemical stability, and provides abundant active sites for the gain and loss of electrons of luteolin on the electrode. When applied to the detection of luteolin by an electrochemical method, the response is rapid and the detection result is accurate. Through experimental determination, the minimum detection limit of luteolin is low, and the repeatability and reproducibility are good; at the same time, the invention has good anti-interference performance, and after adding various interfering ions, the variation range of the peak current is less than 5%.

[0011] Preferably, in step (1), the alkaline solution comprises water, an organic solvent and a base; the volume ratio of the water, the organic solvent and the base is (5-7):(18-20):1; more preferably, the volume ratio of the water, the organic solvent and the base is 6:20:1.

[0012] Preferably, the base comprises aqueous ammonia, and the organic solvent comprises ethanol. More preferably, in step (1), the alkaline solution consists of water, ethanol and aqueous ammonia.

[0013] Preferably, in step (1), the volume ratio of tetraethyl silicate to the alkaline solution is 3:(80-82), more preferably 3:81.

[0014] Preferably, in the step (1), the mass volume ratio of the dopamine hydrochloride to the tetraethyl silicate is 1 g:(9-11), more preferably 1 g:10 mL.

[0015] Preferably, in step (1), the calcination temperature is 850°C-950°C, and the time is 2.5h-3.5h; more preferably, the calcination temperature is 900°C, and the time is 3h.

[0016] Preferably, in step (1), the stirring time is 1h-2h, and the continued stirring time is 10h-14h; the heating rate during calcination is 2.8°C / min-3.2°C / min; more preferably, the stirring time is 1h, and the continued stirring time is 12h; the heating rate during calcination is 3°C / min.

[0017] Preferably, in step (1), the etching is performed using a sodium hydroxide solution, and the etching time is 24h-48h; more preferably, the concentration of the sodium hydroxide solution is 4 mol / L.

[0018] Preferably, in the step (2), the mass ratio of the 2-methylimidazole to the N-doped hollow carbon spheres is 1:(4.5-5.5), more preferably 1:5.

[0019] Preferably, in step (2), the solvent includes water and an organic solvent; the organic solvent includes ethanol; the volume ratio of the water to the organic solvent is (1-2):(1-2), more preferably 1:1.

[0020] More preferably, the solvent consists of water and ethanol, and the mass volume ratio of the N-doped hollow carbon spheres to the solvent is 0.3 g: (45-55) mL, more preferably 0.3 g: 50 mL.

[0021] Preferably, in step (2), the temperature of the rotary evaporation is 55°C-65°C, and the time is 1h-2h; the temperature of the continued rotary evaporation is 55°C-65°C, and the time is 1.5h-2.5h; more preferably, the temperature of the rotary evaporation is 60°C, and the time is 1.5h; the temperature of the continued rotary evaporation is 60°C, and the time is 2h.

[0022] Preferably, the mass ratio of the 2-methylimidazole to the zinc source is 1:(1.1-1.2), more preferably 1:1.

[0023] Preferably, in step (2), the zinc source comprises zinc nitrate; more preferably, the zinc source is added in the form of an aqueous solution.

[0024] Preferably, in the step (2), the mass volume ratio of the 2-methylimidazole to the triethylamine is (0.5-0.7) g:1 mL, more preferably 0.6 g:1 mL.

[0025] Preferably, in step (2), the temperature of the constant temperature heating is 55°C-65°C, and the time is 6h-8h; more preferably, the temperature of the constant temperature heating is 60°C, and the time is 6h.

[0026] In a second aspect, the present invention provides a composite carbon nanomaterial prepared by the above-mentioned method for preparing the composite carbon nanomaterial.

[0027] In a third aspect, the present invention provides application of the composite carbon nanomaterial in the detection of luteolin.

[0028] In a fourth aspect, the present invention provides an electrode for detecting luteolin, wherein the electrode comprises the composite carbon nanomaterial.

[0029] Preferably, the preparation method of the electrode comprises the following steps: polishing, rinsing and drying a bare glassy carbon electrode (GCE), drop-coating a mixed solution of the composite carbon material and water, isopropanol and nafion onto the surface of the dried bare glassy carbon electrode, and drying to obtain the electrode.

[0030] The present invention has the following beneficial effects: This paper develops a composite carbon nanomaterial based on N-doped hollow carbon spheres and ZIF-8, which is fast, accurate and convenient for electrochemical sensing detection of luteolin. The preparation method of the composite carbon nanomaterial of the present invention is simple, and the N-doped hollow carbon spheres are prepared by a hard template method, and then ZIF-8 is grown on the outside and inside of the N-doped hollow carbon spheres by an in-situ growth method. The obtained composite carbon material has high conductivity, high porosity and specific surface area, and has excellent chemical stability. When applied to the detection of luteolin by electrochemical method, it is simple to operate, low cost, high reliability, and fast response speed, which greatly reduces the detection cost and improves the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the process of preparing the composite carbon material in Example 1;

[0032] Figure 2 : are electron microscope images of NC and NC@ZIF-8 composite materials prepared in Example 1; wherein a and b are TEM images of NC@ZIF-8 composite materials, c is a SEM image of NC@ZIF-8 composite materials, and d is a SEM image of NC;

[0033] Figure 3 XRD pattern of the NC@ZIF-8 composite material prepared in Example 1;

[0034] Figure 4 The XPS spectrum of the NC@ZIF-8 composite material prepared in Example 1; wherein a is the overall XPS spectrum of the NC@ZIF-8 composite material, and b, c, and d are high-resolution spectra of C1s, O1s, and N1s, respectively;

[0035] Figure 5The electrochemical test results of the NC@ZIF-8 / GCE electrode are shown in Figure 1. (a) is the DPV diagram of NC@ZIF-8 / GCE detecting 10 μM luteolin at different pH values, (b) is the linear relationship diagram corresponding to the DPV diagram, (c) is the CV curve diagram of NC@ZIF-8 / GCE at different scan rates, and (d) is the linear relationship between the peak current and the scan rate corresponding to the CV curve diagram.

[0036] Figure 6 The electrochemical performance test diagrams of GCE, NC / GCE, ZIF-8 / GCE, and NC@ZIF-8 / GCE; (a) shows the electrochemical performance of each electrode in 5 mM [Fe(CN)6] 3- / 4- Qt curve in solution, (b) Qt curve corresponding to Qt 1 / 2 Figure 2 (c) shows the GCE, NC / GCE, ZIF-8 / GCE, and NC@ZIF-8 / GCE in the presence of 5 mM [Fe(CN)6] 3- / 4- and CV comparison in 0.1M KCl solution;

[0037] Figure 7 (a) is the DPV curve of different concentrations of luteolin on the NC@ZIF-8 / GCE electrode, (b) is the linear relationship between the concentration and the peak current corresponding to the DPV curve;

[0038] Figure 8 The repeatability and reproducibility results of NC@ZIF-8 / GCE electrode are shown in Figure 2.

[0039] Fig. 9 This is the test result of the anti-interference ability of NC@ZIF-8 / GCE electrode. DETAILED DESCRIPTION

[0040] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be understood by those skilled in the art that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] Unless otherwise specified, the experimental methods used in the examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0042] Experimental materials: 98% ethanol, deionized water, 28% ammonia water, 98% tetraethyl silicate (purchased from McLean), 98% dopamine hydrochloride (purchased from McLean), sodium hydroxide (NaOH analytical grade), 2-methylimidazole (purchased from McLean), zinc nitrate hexahydrate (Zn(NO3)2 6H2O), triethylamine, isopropanol (analytical grade), 5% nafion, phosphate buffer solution (PBS, 0.1M; used as buffer for subsequent electrochemical tests) was prepared with Na2HPO4 and NaH2PO4 as raw materials, and pH was adjusted with H3PO4 and KOH. The reagents were not further purified, and all solutions were prepared with deionized water.

[0043] Example 1

[0044] A method for preparing a composite carbon nanomaterial comprises the following steps:

[0045] (1) 300 mL of ethanol, 90 mL of deionized water and 15 mL of ammonia water were stirred at room temperature for 30 min to obtain an alkaline solution, and then 15 mL of tetraethyl silicate was added to the alkaline solution and stirred vigorously for 1 h, and then 1.5 g of dopamine hydrochloride was added and stirred for 12 h, centrifuged and dried, and the obtained product was placed in a tube furnace and heated to 900 ° C at a rate of 3 ° C / min, kept warm for 3 h, and then placed in a 4 mol / L NaOH solution for etching for 24 h to etch away SiO2 to obtain N-doped hollow carbon spheres (NC);

[0046] (2) 0.06 g of 2-methylimidazole and 0.3 g of the N-doped hollow carbon spheres obtained in step (1) were placed in a 100 mL single-mouth round-bottom flask, and then 25 mL of deionized water and 25 mL of ethanol were added, ultrasonically dispersed, and rotary evaporated at 60° C. for 1.5 h on a rotary evaporator. Then 0.06 g of zinc nitrate hexahydrate and 3 mL of deionized water were added to the flask, and the rotary evaporation was continued for 2 h. 100 μL of triethylamine was added, and the mixture was heated and evaporated at a constant temperature of 60° C. in a water bath for 6 h. The ethanol and water were cross-washed, centrifuged, and dried to obtain the composite carbon nanomaterial (NC@ZIF-8).

[0047] Example 2

[0048] The difference between the preparation method of the composite carbon nanomaterial of this embodiment and that of embodiment 1 is that in step (2), the mass ratio of 2-methylimidazole to N-doped hollow carbon spheres is 1:4.5, and the rest is the same as that of embodiment 1 to prepare the composite carbon nanomaterial of this embodiment.

[0049] Example 3

[0050] The difference between the preparation method of the composite carbon nanomaterial of this embodiment and that of embodiment 1 is that in step (2), the mass ratio of 2-methylimidazole to N-doped hollow carbon spheres is 1:5.5, and the rest is the same as that of embodiment 1 to prepare the composite carbon nanomaterial of this embodiment.

[0051] Comparative Example 1

[0052] The difference between the preparation method of the nanomaterial in this comparative example and that in Example 1 is that step (2) is not performed, that is, the N-doped hollow carbon sphere (NC) obtained in step (1) is used as the detection material.

[0053] Comparative Example 2

[0054] The preparation method of the nanomaterial in this comparative example is as follows: 0.06 g of 2-methylimidazole is placed in a 100 mL single-mouth round-bottom flask, 25 mL of deionized water and 25 mL of ethanol are added, and ultrasonic dispersion is performed. Then, 0.06 g of zinc nitrate hexahydrate and 3 mL of deionized water are added to the flask, and rotary evaporation is performed for 2 h. 100 μL of triethylamine is added, and constant temperature evaporation is performed in a water bath at 60° C. for 6 h. The nanomaterial is cross-washed with ethanol and water, and centrifuged and dried to obtain ZIF-8. That is, ZIF-8 is used as the detection material in this comparative example.

[0055] The NC@ZIF-8 composite material prepared in Example 1 was characterized by scanning electron microscopy (SEM, Hitachi SU8220) and transmission electron microscopy (TEM, JEOLjeem-2100). Figure 2 As shown, Figure 2 (a) (b) are TEM images of NC@ZIF-8 composite materials, and (c) (d) are SEM images of NC@ZIF-8 composite materials. Figure 2 In (a), it can be observed that the surface of the hollow carbon sphere is very regular, without other impurities attached, and the carbon sphere is obvious, indicating that the process of synthesizing carbon spheres is successful; Figure 2 As can be seen in (b), some crystals are attached to the surface of the hollow carbon sphere. The crystals present a regular octahedral structure, which is consistent with the morphology of ZIF-8 in the literature. It can be concluded that the process of synthesizing ZIF-8 by in situ growth method of hollow carbon spheres is successful, and the synthesized crystals grow irregularly on the surface of the hollow carbon spheres. Figure 2 It can be seen in (c) that the surface of the hollow carbon sphere is covered with crystals. The crystals are attached very evenly, not only on the surface of the hollow carbon sphere, but also in small amounts inside the hollow carbon sphere. This is because some spheres will crack during the experiment, allowing crystals to attach inside. Figure 2 (d) is the SEM image of NC. It can be seen that the template of the hollow carbon sphere synthesized by the template method has been completely etched by sodium hydroxide to form a hollow carbon sphere with a neat surface and uniform sphere size, which can correspond to TEM.

[0056] The crystal structure of NC@ZIF-8 was characterized by X-ray diffraction (XRD, Bruker D8 Advance). Figure 3 shown. Figure 3 The NC@ZIF-8 composite material shows that the diffraction peaks at 2θ of 7.29°, 10.34°, 12.69°, 14.66°, 16.38° and 17.99° correspond to the (001), (002), (112), (022), (013) and (222) crystal planes of the ZIF-8 crystal, respectively. This proves that the material was successfully synthesized. However, the diffraction peak of NC was not observed in the figure. The reason may be that compared with the peak of the ZIF-8 crystal, its diffraction peak intensity is relatively low, resulting in the diffraction peak of the hollow carbon sphere being hidden, so it cannot be observed. The XRD diffraction pattern of the NC@ZIF-8 composite material is consistent with the standard cards (PDF#37-1560 and PDF#35-1981), indicating that the material was successfully synthesized.

[0057] The functional groups of NC@ZIF-8 composites were analyzed by XPS. Figure 4 shown; from Figure 4 (a) It can be seen that the composite material contains four elements: C, N, O, and Zn. Figure 4 (b) It can be seen that C1s is divided into five characteristic peaks at 284.6eV, 285.4eV, 286.6eV, 287.8eV, and 289eV. These five peaks represent C=C, CN, CO, C=O, and OC=O, respectively. Figure 4 (c) shows the existence form of O1s, which represents C=O, C-OH and CO bonds at 531.4 eV, 532.3 eV and 533.4 eV respectively. Figure 4 (d) shows the fitting of pyridinic N, pyrrolic N and graphitic N at the positions of 398.2 eV, 399.9 eV and 500.9 eV.

[0058] The obtained carbon composite material was made into an electrode and an electrochemical test was carried out for luteolin detection. A method for preparing an electrode for luteolin detection comprises the following steps: polishing the bare GCE with α-Al2O3 powder (0.05 μm), rinsing with ultrapure water and ethanol, and finally drying with nitrogen. 3 mg of the NC@ZIF-8 composite material prepared in Example 1 was put into a 1 mL centrifuge tube, and 600 μL of deionized water, 350 μL of isopropanol, and 50 μL of 5% nafion were measured with a pipette, and ultrasonicated for 5 minutes to obtain a mixed solution. Then 5 μL of the obtained mixed solution was slowly dripped onto the surface of GCE and dried naturally to obtain the electrode NC@ZIF-8 / GCE.

[0059] The electrochemical experiments were carried out on a CHI 660E electrochemical workstation (CH Instrument, USA). A typical three-electrode system was used, with the electrode NC@ZIF-8 / GCE prepared above for luteolin detection as the working electrode, platinum wire as the auxiliary electrode, and saturated Ag / AgCl as the reference electrode. During the experiment, a series of electrochemical analyses of NC@ZIF-8 / GCE were performed using chronocoulometry (CC), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and other methods. The CC experiment was carried out in the range of 0V to 0.25V; the CV experiment was carried out in the range of 0.1 to 0.8V; and the DPV was carried out in the range of -0.2 to 1.0V.

[0060] Figure 5 a is the DPV graph of 10 μM luteolin detected by NC@ZIF-8 / GCE electrode under different pH conditions. It can be seen from the figure that pH value has a strong influence on the peak potential of the detected electrochemical signal. It can be seen from the figure that both Epa and Ip change with the change of pH value. When the pH value increases from 3 to 7, Epa moves toward the negative direction of potential. The peak potential has a good linear response relationship with pH value. Figure 5 b It can be seen that there is a good linear relationship between the two: E pa =-0.0582pH+0.6958(R 2 =0.992), the slope of the equation is 58.2mV / pH, which is close to the theoretical value of 59mV / pH in the Nernst equation, indicating that the number of protons participating in the reaction is equal to the number of electrons transferred in the reaction. In order to further study the electrochemical behavior of the redox reaction of luteolin on the NC@ZIF-8 / GCE electrode, the CV method was used to study the effect of different scan rates on the electrochemical peak current in the range of 30mV / s to 210mV / s. Figure 5 It can be observed in c that with the increase of scan rate, the oxidation peak current and reduction peak current of the redox reaction show a very good positive growth trend with the scan rate v. Through the analysis of this trend, the electrochemical behavior of luteolin on the NC@ZIF-8 / GCE electrode is mainly controlled by the adsorption process. Figure 5 d shows the relationship between v and oxidation peak current (I pa ) is as follows: pa =0.07489v-0.49465(R 2 =0.995); At the same time, there is a good linear fitting relationship between the scan rate v and the reduction peak current, and the linear equation is: I pa =-0.0456v-0.03747(R 2 =0.998).

[0061] Using a method similar to the preparation of the electrode NC@ZIF-8 / GCE, the materials of Comparative Examples 1 and 2 supported the corresponding electrodes NC / GCE and ZIF-8 / GCE, and the electrochemical performance was tested. Figure 6 c shows the CV comparison curves of four modified electrodes using GCE, NC / GCE, ZIF-8 / GCE, and NC@ZIF-8 / GCE. The figure shows that NC@ZIF-8 / GCE has the largest redox peak, indicating that the electrochemical performance of NC@ZIF-8 / GCE is better than that of the bare electrode and the electrode modified with the intermediate product.

[0062] In order to study the effective area of ​​different modified electrodes, Figure 6 In a, the CC method was used to compare four different modified electrodes and the Q and t 1 / 2 The linear relationship ( Figure 6 b) And calculate the effective area (A) of the four different electrodes according to Anson equation: Q = 2nFAcD 1 / 2 t 1 / 2 / п 1 / 2 +Q dl +Q ads .

[0063] Where F is the Faraday constant, the value is: 96500C / mol, the substrate concentration c is 5×10 -6 mol / cm 3 , D is the standard diffusion coefficient, which is 7.6×10 -6 cm 2 / s.Q dl is the double layer charge, Q ads is the Faraday charge, and n is the number of electron transfers, which is 2 according to the previous calculation. Therefore, the effective area of ​​the electrode can be calculated according to this equation. The active surface areas of GCE, NC / GCE, ZIF-8 / GCE, and NC@ZIF-8 / GCE are 0.0072 cm 2 、0.0472cm 2 、0.0910cm 2 and 0.0943cm 2 Therefore, the effective area of ​​NC@ZIF-8 / GCE electrode is significantly larger than that of the other three electrodes, which is more conducive to the enrichment of luteolin.

[0064] Figure 7 The DPV curves of different concentrations of luteolin on the NC@ZIF-8 / GCE electrochemical electrode (a) and the corresponding linear relationship between concentration and peak current (b). Figure 7As can be seen in a: As the concentration of luteolin increases from 0.05μM to 30μM, the oxidation peak current of the DPV analysis method gradually increases. The oxidation peak current (Ipa) and the concentration of luteolin (c) show a very good linear relationship. Figure 7 b: I pa (μA)=0.99433c(μM)+0.92699,R 2 =0.9997. The detection limit (LOD, S / N=3) of the composite material for luteolin is 0.011μM. The experimental results show that the prepared NC@ZIF-8 / GCE has a relatively good linear concentration range and a low detection limit, and can be used for specific practical applications.

[0065] Figure 8 The repeatability and reproducibility of NC@ZIF-8 / GCE electrode were investigated using differential pulse voltammetry. One NC@ZIF-8 / GCE was prepared and 10μM luteolin was tested 8 times to study the repeatability of the electrode; to study the reproducibility of NC@ZIF-8 / GCE, 8 NC@ZIF-8 / GCE electrodes were prepared to test 10μM luteolin. The results showed that the RSDs of repeatability and reproducibility were 2.62% and 1.26%, respectively. The results show that the NC@ZIF-8 / GCE electrode has good repeatability and reproducibility and has good potential application value.

[0066] The anti-interference ability of NC@ZIF-8 composite materials in detecting luteolin was evaluated by DPV test. Fig. 9 shown. Fig. 9 The optimal conditions were shown in the PBS buffer solution (0.1 M) containing 10 μM luteolin and 500 times the amount of K + , Cl - Mg 2+ 、Na + 、NO3 - , 300 times of glucose, fructose, ascorbic acid, mannitol and citric acid; and compared with the blank control group without interfering substances, the results showed that after adding various interfering ions, the change range of peak current was less than 5%, which was within the normal range. The experimental conclusion is that the presence of these ions has no obvious interference with the detection of luteolin, and the NC@ZIF-8 composite material of the present invention can be applied to the detection of luteolin in complex samples.

[0067] The NC@ZIF-8 composite materials prepared in Example 2 and Example 3 have similar structures and can still be applied to the detection of luteolin.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite carbon nanomaterial, It is characterized in that The following steps are involved: (1) stirring tetraethyl silicate in an alkaline solution, adding dopamine hydrochloride and continuing stirring, centrifuging, drying, calcining, and etching to obtain N-doped hollow carbon spheres; (2) 2-methylimidazole and the N-doped hollow carbon spheres obtained in step (1) are uniformly mixed in a solvent, rotary evaporated, and then a zinc source is added, the rotary evaporated is continued, triethylamine is added, the mixture is heated at a constant temperature, washed, centrifuged, and dried to obtain the composite carbon nanomaterial.

2. The method for preparing the composite carbon nanomaterial according to claim 1, It is characterized in that In the step (1), the mass volume ratio of the dopamine hydrochloride to the tetraethyl silicate is 1 g: (9-11) mL.

3. The method for preparing the composite carbon nanomaterial according to claim 1, It is characterized in that In the step (1), the calcination temperature is 850°C-950°C, and the calcination time is 2.5h-3.5h.

4. The method for preparing the composite carbon nanomaterial according to claim 1, It is characterized in that The step (1) satisfies at least one of the following: (1-1) The alkaline solution comprises water, an organic solvent and a base, and the volume ratio of the water, the organic solvent and the base is (5-7): (18-20): 1; (1-2) the volume ratio of the tetraethyl silicate to the alkaline solution is 3:(80-82); (1-3) The stirring time is 1h-2h; (1-4) The stirring time is 10h-14h; (1-5) The heating rate during calcination is 2.8°C / min-3.2°C / min; (1-6) The etching is performed using a sodium hydroxide solution, and the etching time is 24h-48h.

5. The method for preparing the composite carbon nanomaterial according to claim 1, It is characterized in that In the step (2), the mass ratio of the 2-methylimidazole to the N-doped hollow carbon spheres is 1:(4.5-5.5).

6. The method for preparing the composite carbon nanomaterial according to claim 1, It is characterized in that In the step (2), the mass ratio of the 2-methylimidazole to the zinc source is 1:(1.1-1.2), and the mass volume ratio of the 2-methylimidazole to the triethylamine is (0.5-0.7) g:1 mL.

7. The method for preparing the composite carbon nanomaterial according to claim 1, It is characterized in that The step (2) satisfies at least one of the following: (2-1) The solvent includes water and an organic solvent, and the organic solvent includes ethanol; (2-2) The mass volume ratio of the N-doped hollow carbon spheres to the solvent is 0.3 g: (45-55) mL; (2-3) The rotary evaporation temperature is 55°C-65°C and the time is 1h-2h; (2-4) the temperature of the continued rotary evaporation is 55°C-65°C, and the time is 1.5h-2.5h; (2-5) The zinc source includes zinc nitrate; (2-6) The temperature of the constant temperature heating is 55°C-65°C, and the time is 6h-8h.

8. The composite carbon nanomaterial obtained by the method for preparing the composite carbon nanomaterial according to any one of claims 1 to 7.

9. Use of the composite carbon nanomaterial according to claim 8 in the detection of luteolin.

10. An electrode for detecting luteolin, It is characterized in that The electrode comprises the composite carbon nanomaterial according to claim 8.

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