Preparation method of transition metal nitrogen-carbon nano composite material and application of transition metal nitrogen-carbon nano composite material in detection of hydroquinone

Abstract

The invention provides a preparation method of a transition metal nitrogen-carbon nano composite material and application of the transition metal nitrogen-carbon nano composite material in detection of hydroquinone, and belongs to the technical field of composite material preparation.The preparation method comprises the steps that a cobalt nitrate solution and a 2-methylimidazole solution are mixed and fully react, and a mixed solution is obtained; carrying out solid-liquid separation on the mixed solution, and then washing and drying to obtain ZIF-67; dispersing polyacrylonitrile and polystyrene in an organic solvent together, and then adding the ZIF-67 to obtain a spinning solution; performing electrostatic spinning on the spinning solution to obtain a fiber membrane; the fiber membrane is subjected to pre-oxidation treatment and then calcined, a calcined product is cooled and then ground, and the transition metal nitrogen carbon nano composite material Co (at) NC is obtained. The nano composite material prepared by the method can quickly, simply, conveniently and sensitively detect hydroquinone, realizes quantitative analysis of HQ, and solves the problems that the existing HQ detection depends on large-scale instruments and equipment, the pretreatment time is long, the operation is tedious and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material preparation, and particularly relates to a preparation method of a transition metal nitrogen-carbon nanocomposite material and its application in the detection of hydroquinone. Background Art

[0002] Hydroquinone (HQ) is a phenolic compound that is widely used in the fields of medicine, dyes, rubber, pesticides, and papermaking. HQ has high toxicity and low degradability, and it is very easy to pollute the natural environment during the production and application processes. HQ can be bioaccumulated and transmitted through the food chain. After entering the human body through the mouth, nose, or skin, it can cause skin inflammation, nausea, headache, edema, exhaustion, and may even lead to death. In addition, high concentrations of HQ in the environment can cause serious ecological problems. Therefore, it is of great significance to develop a simple and sensitive method for determining the concentration of HQ in water environment.

[0003] At present, the methods for detecting HQ mainly include high-performance liquid chromatography, fluorescence method, and electrochemical method, etc. However, these methods have the disadvantages of complex sample pretreatment, expensive instruments, and time-consuming testing, making on-site timely detection challenging. In recent years, colorimetric detection has attracted much attention due to its advantages such as low cost, simple operation, and visualization. The key challenge in colorimetric analysis lies in selecting a specific catalyst that can effectively oxidize the substrate and cause a significant color change. Natural enzymes exhibit high catalytic efficiency and specificity under mild conditions. However, natural enzymes are expensive, and their activity is highly dependent on environmental conditions such as temperature, pH value, and humidity, which severely limits the practical application of enzymes. Therefore, it is particularly crucial to develop substitutes that can overcome the limitations of natural enzymes and have high catalytic performance.

[0004] Metal-organic framework (MOF) materials are porous nanocrystalline materials assembled by bridging metal nodes with organic ligands. Using MOF as a sacrificial template, MOF-based derivatives with good dispersibility and many active sites can be prepared by oxidation or carbonization, including metal oxides, metal carbides, metal nitrides, and metal nitrogen carbides. Among them, the high specific surface area and porosity of transition metal nitrogen-carbon materials ensure the accessibility of catalytic active sites and exhibit excellent electron and proton transport properties, and are considered to be very promising catalysts in different fields. However, high temperature may cause the collapse of the MOF structure, resulting in some active sites being unable to participate in the reaction. Summary of the Invention

[0005] To solve the problems of complex operation, high cost and difficulty in immediate detection existing in the existing HQ detection methods, the present invention provides a preparation method of a transition metal-nitrogen-carbon nanocomposite. The nanocomposite prepared by this method can rapidly, simply and sensitively detect hydroquinone, realize the quantitative analysis of HQ, and solve the problems such as the dependence on large-scale instrument equipment, long pretreatment time and cumbersome operation in the current HQ detection.

[0006] The present invention also provides a transition metal-nitrogen-carbon nanocomposite and its application in the detection of hydroquinone.

[0007] The present invention is realized through the following technical solutions:

[0008] The present invention provides a preparation method of a transition metal-nitrogen-carbon nanocomposite, and the preparation method includes:

[0009] Mix a cobalt nitrate solution and a 2-methylimidazole solution, and fully react to obtain a mixed solution;

[0010] Perform solid-liquid separation on the mixed solution, then perform washing and drying to obtain ZIF-67;

[0011] Disperse polyacrylonitrile and polystyrene together in an organic solvent, and then add the ZIF-67 to obtain a spinning solution;

[0012] Perform electrospinning on the spinning solution to obtain a fibrous membrane;

[0013] Perform pre-oxidation treatment on the fibrous membrane, then perform calcination, and grind the calcined product after cooling to obtain a transition metal-nitrogen-carbon nanocomposite Co@NC.

[0014] Further, the mixing of the cobalt nitrate solution and the 2-methylimidazole solution, and fully reacting to obtain a mixed solution specifically includes:

[0015] Dissolve cobalt nitrate in a mixed solvent of methanol and ethanol to obtain a cobalt nitrate solution;

[0016] Dissolve 2-methylimidazole in the mixed solvent to obtain a 2-methylimidazole solution;

[0017] Mix the cobalt nitrate solution and the 2-methylimidazole solution, and react for 24 ± 4 h to obtain a mixed solution.

[0018] Further, in the mixed solvent, the volume ratio of methanol to ethanol is 1:1;

[0019] In the mixed solution, the molar ratio of cobalt nitrate to 2-methylimidazole is 1:3.9;

[0020] In the mixed solution, the concentration of cobalt nitrate is 0.06 - 0.08 mol / L.

[0021] Further, subject the mixture to solid-liquid separation, followed by washing and drying to obtain ZIF-67, which specifically includes:

[0022] Subject the mixture to solid-liquid separation, wash the obtained solid several times with ethanol, and then dry it at 60 ± 10 °C to obtain ZIF-67.

[0023] Further, co-disperse polyacrylonitrile and polystyrene in an organic solvent, and then add the ZIF-67 to obtain a spinning solution, which specifically includes:

[0024] Co-disperse polyacrylonitrile and polystyrene in N,N-dimethylformamide, then add the ZIF-67 and stir for 12 ± 2 h to obtain a spinning solution;

[0025] Among them, the mass ratio of polyacrylonitrile, polystyrene and the ZIF-67 in the spinning solution is 2:1:1;

[0026] The concentration of the ZIF-67 in the spinning solution is 0.05 g / mL.

[0027] Further, subject the spinning solution to electrospinning to obtain a fiber membrane, which specifically includes:

[0028] Subject the spinning solution to electrospinning, with the positive voltage for electrospinning being 18 kV, the negative voltage for electrospinning being -2 kV, and the injection rate being 1 mL / h to obtain a fiber membrane.

[0029] Further, subject the fiber membrane to pre-oxidation treatment, followed by calcination. After the calcination product is cooled, grind it to obtain a transition metal nitrogen-carbon nanocomposite Co@NC, which specifically includes:

[0030] Pre-oxidize the fiber membrane at 200 ± 20 °C for 1 - 3 h, then under an inert atmosphere, heat it to 500 ± 50 °C at a heating rate of 5 ± 1 °C / min, hold for 1 - 3 h, and then heat it to 800 ± 50 °C at a heating rate of 1 - 3 °C / min and calcine for 1 - 3 h. After the calcination product is naturally cooled, grind it to obtain a transition metal nitrogen-carbon nanocomposite Co@NC.

[0031] Based on the same inventive concept, the present invention provides a transition metal nitrogen-carbon nanocomposite, which is prepared by the preparation method of the above-mentioned transition metal nitrogen-carbon nanocomposite.

[0032] Based on the same inventive concept, the present invention provides an application of the transition metal nitrogen-carbon nanocomposite in detecting hydroquinone.

[0033] Based on the same inventive concept, the present invention provides an application of a transition metal nitrogen-carbon nanocomposite material in the preparation of a hydroquinone detection reagent.

[0034] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0035] 1. In the preparation method of a transition metal nitrogen-carbon nanocomposite material of the present invention, zeolitic imidazolate framework material ZIF-67 is prepared by a room temperature co-precipitation method, and then dispersed with polyacrylonitrile (PAN) and polystyrene (PS) in N,N-dimethylformamide (DMF), and PAN / PS / ZIF-67 composite nanofibers are prepared by an electrospinning method. Subsequently, metal cobalt nitrogen-carbon (Co@NC) nanocomposite material is obtained through pre-oxidation and high-temperature calcination. This material can oxidize colorless 3,3,5,5-tetramethylbenzidine (TMB) into blue oxTMB, and the presence of hydroquinone (HQ) can inhibit the oxidation of TMB. Along with the gradual fading of the blue solution, colorimetric detection of HQ can be achieved.

[0036] 2. A transition metal nitrogen-carbon nanocomposite material of the present invention can rapidly, simply and sensitively detect hydroquinone. By using the color change caused by the oxidation-reduction reaction of 3,3,5,5-tetramethylbenzidine (TMB) and hydroquinone (HQ) on the surface of Co@NC, quantitative analysis of HQ can be realized, solving the problems that the current detection of HQ relies on large-scale instrument equipment, has a long pre-treatment time, is cumbersome to operate and cannot be detected immediately. Among them, the carbon nanofiber material PAN / PS with a one-dimensional morphology can stabilize the MOF material ZIF-67, avoiding the collapse of the ZIF-67 structure, thereby making full use of the catalytic activity of ZIF-67 and the high specific surface area of carbon fiber, and improving the stability and reaction efficiency of the catalyst.

[0037] 3. A transition metal nitrogen-carbon nanocomposite material of the present invention. The colorimetric detection method established based on this nanocomposite material can rapidly, simply and sensitively detect the concentration of HQ. By means of the color change caused by the oxidation-reduction reaction of TMB, quantitative analysis of HQ can be realized. In only 10 minutes, the concentration of HQ can be visually judged according to the depth of the color with the naked eye, and the concentration of HQ in the solution can be further accurately analyzed with the help of an ultraviolet-visible spectrophotometer. Combining the advantages of visual evaluation and instrument detection can provide rapid and reliable HQ detection results. Description of the Drawings

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0039] Figure 1 This is the mechanism diagram of Co@NC colorimetric detection of HQ in the present invention.

[0040] Figure 2 This is the microstructure diagram of Co@NC and PAN / PS / ZIF nanofibers in the present invention: Among them, (A) FESEM image of PAN / PS / ZIF nanofibers; (B) FESEM image of PAN / PS / ZIF nanofibers after pre-oxidation; (C) FESEM image of PAN / PS / ZIF nanofibers after pre-oxidation and calcination; (D) TEM image of Co@NC; (E, F) HRTEM images of Co@NC.

[0041] Figure 3 These are the XRD and Raman diagrams of NC and Co@NC: Among them, (A) XRD diagrams of NC and Co@NC; (B) Raman diagrams of NC and Co@NC.

[0042] Figure 4 These are the oxidation activity of Co@NC and influencing factors: Among them, (A) UV-visible spectra of TMB, Co@NC and their mixed solutions; (B) Influence of pH on the oxidation activity of Co@NC; (C) Influence of Co@NC on the oxidation activity of Co@NC; (D) Influence of TMB concentration on the oxidation activity of Co@NC.

[0043] Figure 5 These are the quantitative detection of HQ by Co@NC: Among them, (A) UV-visible spectra of the Co@NC-TMB system at different HQ concentrations; (B) Linear relationship diagram between absorbance value and HQ concentration.

[0044] Figure 6 These are the comparison diagrams of Co@NC and C3N4-ZIF: Among them, (A) UV-visible spectra of oxidation activity; (B) UV-visible spectra after adding HQ. Detailed implementation manners

[0045] The following will specifically elaborate on the present invention in combination with the detailed implementation manners and embodiments, and the advantages and various effects of the present invention will be presented more clearly therefrom. Those skilled in the art should understand that these detailed implementation manners and embodiments are used to illustrate the present invention, rather than limiting the present invention.

[0046] Throughout the specification, unless otherwise specifically stated, the terms used herein shall be understood to have the meanings as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention pertains. In case of any contradiction, this specification shall prevail.

[0047] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0048] Unless otherwise specifically stated, the experimental methods used in the following examples are all conventional methods.

[0049] The technical principle of the present invention is as follows:

[0050] The present invention provides a method for preparing a transition metal-nitrogen-carbon nanocomposite, and the preparation method includes:

[0051] S1. Mix a cobalt nitrate solution and a 2-methylimidazole solution, and react fully to obtain a mixed solution;

[0052] S2. Perform solid-liquid separation on the mixed solution, then wash and dry it to obtain ZIF-67;

[0053] S3. Disperse polyacrylonitrile and polystyrene together in an organic solvent, and then add the ZIF-67 to obtain a spinning solution;

[0054] S4. Perform electrospinning on the spinning solution to obtain a fiber membrane;

[0055] S5. Perform pre-oxidation treatment on the fiber membrane, then perform calcination, and grind the calcined product after cooling to obtain the transition metal-nitrogen-carbon nanocomposite Co@NC.

[0056] Step S1 specifically includes:

[0057] Dissolve cobalt nitrate in a mixed solvent of methanol and ethanol to obtain a cobalt nitrate solution;

[0058] Dissolve 2-methylimidazole in the mixed solvent to obtain a 2-methylimidazole solution;

[0059] Mix the cobalt nitrate solution and the 2-methylimidazole solution, and react for 24 ± 4 h to obtain a mixed solution.

[0060] In the mixed solvent, the volume ratio of methanol to ethanol is 1:1;

[0061] In the mixed solution, the molar ratio of cobalt nitrate to 2-methylimidazole is 1:3.9;

[0062] In the mixed solution, the concentration of cobalt nitrate is 0.06 - 0.08 mol / L.

[0063] Step S2 specifically includes:

[0064] Perform solid-liquid separation on the mixed solution, wash the obtained solid several times with ethanol, and then dry it at 60 ± 10 °C to obtain ZIF-67.

[0065] Step S3 specifically includes:

[0066] Disperse polyacrylonitrile and polystyrene in N,N-dimethylformamide together, and then add the ZIF-67 and stir for 12 ± 2 h to obtain a spinning solution;

[0067] Among them, the mass ratio of polyacrylonitrile, polystyrene and the ZIF-67 in the spinning solution is 2:1:1;

[0068] The concentration of the ZIF-67 in the spinning solution is 0.05 g / mL.

[0069] In the present invention, the mass ratio of polyacrylonitrile, polystyrene and the ZIF-67 in the spinning solution is 2:1:1, and the amount of ZIF-67 is relatively moderate. If the content of ZIF-67 is too small, there are fewer Co active sites after calcination, and the activity of catalyzing the oxidation of TMB is not high; if the content of ZIF-67 is too much, it is easy to cause the aggregation of active sites after calcination, and its catalytic performance cannot be fully exerted. Among them, polyacrylonitrile and polystyrene both play a role in supporting ZIF-67, and at the same time can disperse ZIF-67 to avoid the aggregation of MOF; polyacrylonitrile has a high nitrogen element content, and polystyrene has stable chemical properties, and as a support material, it can improve the stability of the composite material.

[0070] Step S4 specifically includes:

[0071] Perform electrospinning on the spinning solution, with the positive voltage of electrospinning being 18 kV, the negative voltage of electrospinning being -2 kV, and the injection rate being 1 mL / h to obtain a fiber membrane.

[0072] Step S4 specifically includes:

[0073] Pre-oxidize the fiber membrane at 200 ± 20 °C for 1 - 3 h, then under an inert atmosphere, heat it to 500 ± 50 °C at a heating rate of 5 ± 1 °C / min, keep it warm for 1 - 3 h, and then heat it to 800 ± 50 °C at a heating rate of 1 - 3 °C / min and calcine it for 1 - 3 h. After the calcined product is naturally cooled, it is ground to obtain a transition metal nitrogen-carbon nanocomposite Co@NC.

[0074] In the present invention, the advantage of pre-oxidizing the fiber membrane at 200 ± 20 °C is to enhance the thermal stability of the fibers. If the un-pre-oxidized fiber membrane is directly heated to 800 °C, the fiber membrane may melt or adhere due to thermal decomposition, resulting in the destruction of the surface microtopography.

[0075] In the present invention, the calcination is carried out in two stages. The purpose of calcining at 500 ± 50 °C for 1 - 3 h is to remove organic ligands and adsorbed water in the fiber membrane, and at the same time, initially form a carbon skeleton structure. If directly heated to 800 °C, the rapid gas release may cause the rupture of the fiber structure.

[0076] Then, the advantage of calcining at 800 ± 50 °C for 1 - 3 h is that it can promote the graphitization process, improve the crystallization degree of Co, and at the same time improve the stability of the composite fiber material.

[0077] Next, the preparation method of a transition metal-nitrogen-carbon nanocomposite material of the present invention and its application in the detection of hydroquinone will be described in detail in combination with examples and experimental data.

[0078] Example 1

[0079] This example provides a preparation method of a transition metal-nitrogen-carbon nanocomposite material, which is as follows:

[0080] (1) First, 0.873 g of cobalt nitrate hexahydrate and 0.96 g of 2-methylimidazole are respectively dissolved in 20 mL of a mixed solution of methanol and ethanol (volume ratio 1:1). Subsequently, the two solutions are mixed evenly and stirred at room temperature for 24 hours. The obtained purple precipitate is collected by centrifugation, washed three times with ethanol, and dried in an oven at 60 °C for one day. The obtained product is denoted as ZIF-67.

[0081] (2) Under stirring conditions, 0.5 g of polyacrylonitrile (PAN) and 0.25 g of polystyrene (PS) are dispersed in 5 mL of N,N-dimethylformamide (DMF). Subsequently, 1 g of ZIF-67 is added to this solution, and the mixture is stirred overnight to obtain a uniform purple solution, which is transferred to a 10 mL syringe for electrospinning. The experimental parameters are as follows: the positive voltage for spinning is 18 kV, the negative voltage for spinning is -2 kV, and the injection rate is 1 mL / h. The PAN / PS / ZIF precursor fibers are collected on a metal roller through a silicon oil paper. Subsequently, the fiber membrane is pre-oxidized at 200 °C for 2 hours, heated to 500 °C at a heating rate of 5 °C / min, maintained for 2 hours in an argon atmosphere, then heated to 800 °C at a heating rate of 2 °C / min, and maintained for another 2 hours. After naturally cooling to room temperature, the black fiber membrane is ground in an agate mortar. The obtained product is denoted as Co@NC.

[0082] The PAN / PS nanofibers were prepared by the same method as in step (2), except that no ZIF-67 nanoparticles were added, and the resulting product was denoted as NC.

[0083] Comparative Example 1

[0084] This example provides a method for preparing a transition metal nitrogen-carbon composite material, which is as follows:

[0085] Weigh 0.291 g of cobalt nitrate hexahydrate and dissolve it in 10 mL of methanol. Weigh 0.656 g of 2-methylimidazole and dissolve it in 15 mL of methanol. Mix the two solutions together, then add 0.25 g of C3N4 (purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.), stir for 24 hours, wash 3 times with methanol, dry overnight at 60 °C, grind the solid sample and calcine it in a tube furnace. Heat it to 350 °C at a rate of 2 °C per minute and hold for 90 min, then heat it to 600 °C at a rate of 2 °C per minute in an argon atmosphere and hold for 2 h, and cool it down to obtain C3N4-ZIF.

[0086] Example 2

[0087] This example verifies the HQ detection performance of the product prepared in Example 1.

[0088] "Turn-off" colorimetric detection of HQ

[0089] (1) Exploration of the oxidation activity of Co@NC

[0090] First, add 0.25 mM 3,3,5,5-tetramethylbenzidine (TMB) and Co@NC material to 0.2 M HAc-NaAc (pH = 3.6) buffer solution in sequence, then incubate at 37 °C for 10 minutes, and detect the absorption peak of the solution at 652 nm by ultraviolet-visible spectrophotometer.

[0091] (2) Colorimetric detection of the concentration of HQ

[0092] Add 0.2 M HAc-NaAc, 10 μg / mL Co@NC, 1 mM TMB and different concentrations of HQ to the cuvette in sequence, then incubate at 37 °C for 10 minutes, record the absorption peaks of different solutions at 652 nm, and establish a linear relationship between different HQ concentrations and absorbance intensities.

[0093] Using the same method, verify the HQ detection performance of C3N4-ZIF prepared in Comparative Example 1.

[0094] The principle of detecting hydroquinone (HQ) by the transition metal nitrogen-carbon (Co@NC) nanofiber material prepared in Example 1 is as Figure 1As shown. It can be seen from the figure that Co@NC can oxidize colorless 3,3,5,5 - tetramethylbenzidine (TMB) into blue oxTMB. This may be because Co exists on the surface of Co@NC 3+ and Co 2+ , and Co 3+ / Co 2+ with a relatively high reduction potential can oxidize TMB and has a strong absorption peak at 652 nm. With the addition of HQ, the blue solution gradually fades because the oxidized oxTMB can oxidize HQ and itself is reduced to colorless TMB. According to the color change caused by different concentrations of HQ, rapid, simple and sensitive analytical detection can be achieved.

[0095] Co@NC was obtained by calcining the zeolitic imidazolate framework material ZIF - 67 after blending it with polyacrylonitrile (PAN) and polystyrene (PS), and its morphology is as Figure 2 shown. It can be seen from Figure (A) that ZIF - 67 is embedded in PAN / PS nanofibers, forming a unique "string of jewels" structure. After pre - oxidation and carbonization, the PAN / PS / ZIF - 67 nanofilm still retains the fibrous structure. To observe its morphology more clearly, the TEM image of Co@NC is given in Figure (D). It can be seen that the internal part of the carbonized ZIF - 67 decomposes into many black Co nanoparticles of different sizes. The high - resolution TEM images are shown in Figures (E - F), and the crystal stripes are clearly visible, indicating that the material has good crystallinity.

[0096] The crystal structures of NC and Co@NC were analyzed by XRD. As Figure 3 (A) shows, all materials have a broad diffraction peak at about 26°, which is attributed to the (002) plane of graphitic carbon. Co@NC nanofibers have three relatively sharp peaks at 44.2°, 51.5° and 75.8° respectively, corresponding to the (111), (200) and (220) crystal planes of Co (JCPDS No.89 - 4307), indicating that the organic ligands of the MOF decompose and Co nanoparticles are formed by the reduction of ZIF - 67 during high - temperature calcination. Raman spectroscopy was used to further study the defect degree and graphitization degree of the nanofibers. It can be seen from Figure 3 (B) that all samples have two strong peaks near 1340 and 1590 cm -1 corresponding to the D band of defective carbon and the G band of ordered graphite sp 2 carbon respectively. The intensity ratio (I D / I G ) of the D and G bands reflects the number of defects and conductive graphite present in the nanofibers. I D / I GThe larger the value, the higher the defect level of the material. Generally speaking, a high degree of graphitization, that is, a low degree of defects, is beneficial to improving the conductivity of carbon materials. In fact, the electron transfer ability of electrode materials has a great impact on the performance of electrochemical sensors. The I of NC and Co@NC D / I G is the same, indicating that the two have similar degrees of crystallization.

[0097] Such as Figure 4 (A), neither TMB nor Co@NC has an absorption peak in the range of 800 - 400 nm, but the mixed solution of the two has an obvious absorption peak at 652 nm, indicating that Co@NC can directly oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB. This may be because Co on the surface of Co@NC 3+ / Co 2+ has a relatively high redox potential, resulting in the oxidation of TMB in acidic Hac-NaAc solution. Subsequently, the influence of the reaction environment on the oxidation activity of Co@NC was explored. As can be seen from Figure (B), the optimal pH value is 3.6. In addition, the concentrations of Co@NC and TMB also affect the oxidation effect of the material on TMB.

[0098] With the addition of HQ, the absorption intensity of oxTMB at 652 nm gradually decreases, as Figure 5 (A) shows. At the same time, Figure 5 the inset in (B) shows that the blue color of the solution gradually fades. This may be because highly oxidized oxTMB oxidizes HQ into benzoquinone (BQ), and itself is reduced to colorless TMB, thus inhibiting the oxidation of TMB and resulting in the disappearance of the blue color. In the range of 0.005 - 0.1 mM, there is a good linear relationship between the absorbance value and the concentration, and the linear equation is ΔA = -8.65C + 0.933 (R 2 = 0.993), where C represents the concentration of HQ, and the detection limit of this method is 11.7 μM.

[0099] From Figure 6 (A) and (B), it can be seen that C3N4-ZIF cannot turn colorless TMB into blue oxTMB. After adding HQ, the color of the mixed solution of Co@NC and TMB fades, while the color of C3N4-ZIF does not change. Therefore, C3N4-ZIF cannot achieve colorimetric detection of HQ. The above results show that Co@NC of the present invention can be used for colorimetric detection of HQ, and this method has not been reported, and the detection performance of the material is also relatively excellent.

[0100] The ZIF-67 material prepared in the present invention forms Co nanoparticles after being calcined at 800 °C. The principle of catalyzing the oxidation of colorless TMB into oxTMB is that Co exists on the surface of Co3+ / Co 2+ , due to Co 3+ / Co 2+ has a relatively high reduction potential and can thus directly oxidize TMB. For the ZIF-67 material prepared in Comparative Example 1, the calcination temperature was 500 °C, which was relatively low and unable to form Co nanoparticles, so it could not undergo a redox reaction with TMB.

[0101] In summary, the present invention has successfully developed a colorimetric detection method for rapidly, simply and sensitively detecting the concentration of HQ. By means of the color change caused by the TMB redox reaction, quantitative analysis of HQ can be achieved. This method has a fast detection speed. It only takes 10 minutes to visually judge the concentration of HQ according to the color depth with the naked eye, and the concentration of HQ in the solution can also be further accurately analyzed with the help of a UV-visible spectrophotometer. Combining the advantages of visual assessment and instrumental detection can provide rapid and reliable results.

[0102] Finally, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0103] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0104] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A method for preparing a transition metal nitrogen-carbon nanocomposite, characterized in that, The preparation method includes: Mix a cobalt nitrate solution and a 2-methylimidazole solution, and react fully to obtain a mixed solution; Perform solid-liquid separation on the mixed solution, then wash and dry it to obtain ZIF-67; Disperse polyacrylonitrile and polystyrene together in an organic solvent, and then add the ZIF-67 to obtain a spinning solution; Perform electrospinning on the spinning solution to obtain a fiber membrane; Perform pre-oxidation treatment on the fiber membrane, then perform calcination, and grind the calcined product after cooling to obtain a transition metal-nitrogen-carbon nanocomposite Co@NC.

2. The preparation method of a transition metal nitride-carbon nanocomposite according to claim 1, characterized in that, The mixing of the cobalt nitrate solution and the 2-methylimidazole solution, and reacting fully to obtain a mixed solution specifically includes: Dissolve cobalt nitrate in a mixed solvent of methanol and ethanol to obtain a cobalt nitrate solution; Dissolve 2-methylimidazole in the mixed solvent to obtain a 2-methylimidazole solution; Mix the cobalt nitrate solution and the 2-methylimidazole solution, and react for 24 ± 4 h to obtain a mixed solution.

3. The preparation method of a transition metal nitride-carbon nanocomposite according to claim 2, characterized in that, In the mixed solvent, the volume ratio of methanol to ethanol is 1:1; In the mixed solution, the molar ratio of cobalt nitrate to 2-methylimidazole is 1:3.9; In the mixed solution, the concentration of cobalt nitrate is 0.06 - 0.08 mol / L.

4. The preparation method of a transition metal nitride-carbon nanocomposite according to claim 1, characterized in that The performing solid-liquid separation on the mixed solution, then washing and drying it to obtain ZIF-67 specifically includes: Perform solid-liquid separation on the mixed solution, wash the obtained solid several times with ethanol, and then dry it at 60 ± 10 °C to obtain ZIF-67.

5. The preparation method of a transition metal-nitrogen-carbon nanocomposite according to claim 1, wherein, The dispersing of polyacrylonitrile and polystyrene together in an organic solvent, and then adding the ZIF-67 to obtain a spinning solution specifically includes: Disperse polyacrylonitrile and polystyrene together in N,N-dimethylformamide, and then add the ZIF-67 and stir for 12 ± 2 h to obtain a spinning solution; Among them, the mass ratio of polyacrylonitrile, polystyrene and the ZIF-67 in the spinning solution is 2:1:1; The concentration of the ZIF-67 in the spinning solution is 0.05 g / mL.

6. The preparation method of a transition metal-nitrogen-carbon nanocomposite according to claim 1, characterized in that, The performing electrospinning on the spinning solution to obtain a fiber membrane specifically includes: Perform electrospinning on the spinning solution, with the positive spinning voltage being 18 kV, the negative spinning voltage being -2 kV, and the injection speed being 1 mL / h to obtain a fiber membrane.

7. The preparation method of a transition metal nitride-carbon nanocomposite according to claim 1, characterized in that, The performing pre-oxidation treatment on the fiber membrane, then performing calcination, and grinding the calcined product after cooling to obtain a transition metal-nitrogen-carbon nanocomposite Co@NC specifically includes: Pre-oxidize the fiber membrane at 200 ± 20 °C for 1 - 3 h, then under an inert atmosphere, heat it to 500 ± 50 °C at a heating rate of 5 ± 1 °C / min, hold for 1 - 3 h, and then heat it to 800 ± 50 °C at a heating rate of 1 - 3 °C / min and calcine for 1 - 3 h. After the calcined product cools naturally, grind it to obtain a transition metal-nitrogen-carbon nanocomposite Co@NC.

8. A transition metal-nitrogen-carbon nanocomposite, characterized in that, The nanocomposite is prepared by the preparation method of a transition metal-nitrogen-carbon nanocomposite according to any one of claims 1 - 7.

9. Use of a transition metal-nitrogen-carbon nanocomposite according to claim 8 in the detection of hydroquinone.

10. Use of a transition metal nitrogen-carbon nanocomposite as described in claim 8 in the preparation of a hydroquinone detection reagent.

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