Preparation method of transition metal nitrogen-carbon nanocomposite and application thereof in detection of hydroquinone

Abstract

The application provides a preparation method of a transition metal nitrogen-carbon nanocomposite and application of the transition metal nitrogen-carbon nanocomposite in detection of hydroquinone, and belongs to the technical field of composite material preparation. The preparation method comprises the following steps: mixing a cobalt nitrate solution and a 2-methyl imidazole solution, fully reacting, and obtaining a mixed solution; performing solid-liquid separation on the mixed solution, then performing washing and drying, and obtaining ZI F-67; dispersing polyacrylonitrile and polystyrene in an organic solvent, then adding the ZI F-67, and obtaining a spinning solution; performing electrostatic spinning on the spinning solution, and obtaining a fiber membrane; performing pre-oxidation treatment on the fiber membrane, then performing calcination, grinding the calcination product after cooling, and obtaining a transition metal nitrogen-carbon nanocomposite Co@NC. The nanocomposite prepared by the method can quickly, simply and sensitively detect hydroquinone, realizes quantitative analysis of HQ, and solves the problems that current HQ detection relies on large-scale instruments and equipment, has a long pretreatment time, and is complicated to operate.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation technology, and specifically relates to a method for preparing a transition metal nitrogen-carbon nanocomposite material and its application in the detection of hydroquinone. Background Technology

[0002] Hydroquinone (HQ) is a phenolic compound widely used in pharmaceuticals, dyes, rubber, pesticides, and papermaking. HQ is highly toxic and has low degradation rates, easily polluting the environment during production and application. HQ can bioaccumulate and be transferred through the food chain; after entering the human body via the mouth, nose, or skin, it can cause skin inflammation, nausea, headache, edema, exhaustion, and even death. Furthermore, high concentrations of HQ in the environment can lead to serious ecological problems. Therefore, developing a simple and sensitive method for determining HQ concentrations in aquatic environments is of great significance.

[0003] Currently, methods for detecting HQ mainly include high-performance liquid chromatography (HPLC), fluorescence methods, and electrochemical methods. However, these methods suffer from drawbacks such as complex sample pretreatment, expensive instruments, and time-consuming testing, making timely on-site detection challenging. In recent years, colorimetric detection has attracted much attention due to its advantages such as low cost, ease of operation, and visualization. A key challenge in colorimetric analysis lies in selecting a specific catalyst that effectively oxidizes the substrate and induces a significant color change. Natural enzymes exhibit high catalytic efficiency and specificity under mild conditions. However, the high cost of natural enzymes and their high dependence on environmental conditions such as temperature, pH, and humidity severely limit their practical applications. Therefore, developing alternatives that overcome the limitations of natural enzymes while possessing highly efficient catalytic performance is crucial.

[0004] Metal-organic frameworks (MOFs) are porous nanocrystalline materials assembled from metal nodes bridging organic ligands. Using MOFs as sacrificial templates, well-dispersed MOF-based derivatives with numerous active sites can be prepared through oxidation or carbonization. These include metal oxides, metal carbides, metal nitrides, and metal nitrides. Among these, transition metal nitrides and carbon materials, with their high specific surface area and porosity, ensure the accessibility of catalytic active sites and exhibit excellent electron and proton transport properties, making them highly promising catalysts in various fields. However, high temperatures can cause MOF structure collapse, preventing some active sites from participating in the reaction. Summary of the Invention

[0005] To address the problems of complex operation, high cost, and difficulty in real-time detection in existing HQ detection methods, this invention provides a method for preparing transition metal nitrogen-carbon nanocomposite materials. The nanocomposite materials prepared by this method can rapidly, easily, and sensitively detect hydroquinone, achieving quantitative analysis of HQ. This solves the problems of current HQ detection relying on large instruments and equipment, long pretreatment time, and cumbersome operation.

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

[0007] This invention is achieved through the following technical solution:

[0008] This invention provides a method for preparing transition metal nitrogen-carbon nanocomposite materials, the method comprising:

[0009] Cobalt nitrate solution and 2-methylimidazole solution were mixed and allowed to react fully to obtain a mixture;

[0010] The mixture was subjected to solid-liquid separation, followed by washing and drying to obtain ZIF-67;

[0011] Polyacrylonitrile and polystyrene were co-dispersed in an organic solvent, and then ZIF-67 was added to obtain a spinning solution;

[0012] The spinning solution is electrospinned to obtain a fiber membrane;

[0013] The fiber membrane was pre-oxidized and then calcined. The calcined product was cooled and then ground to obtain the transition metal nitrogen carbon nanocomposite material Co@NC.

[0014] Furthermore, the step of mixing the cobalt nitrate solution and the 2-methylimidazole solution and allowing them to react fully to obtain a mixed solution specifically includes:

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

[0016] 2-Methylimidazole is dissolved in the mixed solvent to obtain a 2-methylimidazole solution;

[0017] The cobalt nitrate solution and the 2-methylimidazole solution were mixed and reacted for 24±4 h to obtain a mixture.

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

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

[0020] The concentration of cobalt nitrate in the mixture is 0.06–0.08 mol / L.

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

[0022] The mixture was subjected to solid-liquid separation. The resulting solid was washed several times with ethanol and then dried at 60±10℃ to obtain ZIF-67.

[0023] Furthermore, the step of co-dispersing polyacrylonitrile and polystyrene in an organic solvent, followed by the addition of ZIF-67 to obtain the spinning solution, specifically includes:

[0024] Polyacrylonitrile and polystyrene were co-dispersed in N,N-dimethylformamide, and then ZIF-67 was added. The mixture was stirred for 12±2 h to obtain a spinning solution.

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

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

[0027] Furthermore, the step of electrospinning the spinning solution to obtain a fiber membrane specifically includes:

[0028] The spinning solution was subjected to electrospinning with a positive spinning voltage of 18kV, a negative spinning voltage of -2kV, and a feeding rate of 1mL / h to obtain a fiber membrane.

[0029] Furthermore, the fiber membrane is pre-oxidized, then calcined, and the calcined product is cooled and ground to obtain the transition metal nitrogen-carbon nanocomposite material Co@NC, specifically including:

[0030] The fiber membrane was pre-oxidized at 200±20℃ for 1-3 hours, then heated to 500±50℃ at a heating rate of 5±1℃ / min under an inert atmosphere and held for 1-3 hours. It was then heated to 800±50℃ at a heating rate of 1-3℃ / min and calcined for 1-3 hours. After the calcined product cooled naturally, it was ground to obtain the transition metal nitrogen carbon nanocomposite material Co@NC.

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

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

[0033] Based on the same inventive concept, this invention provides an application of transition metal nitrogen-carbon nanocomposite materials in the preparation of hydroquinone detection reagents.

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

[0035] 1. This invention discloses a method for preparing a transition metal nitrogen-carbon nanocomposite material. The method involves preparing a zeolite imidazolium ester framework material ZIF-67 via room temperature co-precipitation, then dispersing it with polyacrylonitrile (PAN) and polystyrene (PS) in N,N-dimethylformamide (DMF). PAN / PS / ZIF-67 composite nanofibers are prepared by electrospinning, followed by pre-oxidation and high-temperature calcination to obtain a cobalt-nitrogen-carbon (Co@NC) nanocomposite material. This material can oxidize colorless 3,3,5,5-tetramethylbenzidine (TMB) to blue oxTMB, while the presence of hydroquinone (HQ) can inhibit the oxidation of TMB. As the blue solution gradually fades, colorimetric detection of HQ can be achieved.

[0036] 2. This invention discloses a transition metal nitrogen-carbon nanocomposite material, which enables rapid, simple, and sensitive detection of hydroquinone. It utilizes the color change caused by the redox reaction of 3,3,5,5-tetramethylbenzidine (TMB) and hydroquinone (HQ) on the Co@NC surface to achieve quantitative analysis of HQ. This solves the problems of current HQ detection methods, which rely on large instruments, have long pretreatment times, are cumbersome, and cannot be detected instantly. The one-dimensional carbon nanofiber material PAN / PS stabilizes the MOF material ZIF-67, preventing ZIF-67 structural collapse, thereby fully utilizing the catalytic activity of ZIF-67 and the high specific surface area of ​​carbon fibers to improve catalyst stability and reaction efficiency.

[0037] 3. This invention relates to a transition metal nitrogen-carbon nanocomposite material. The colorimetric detection method established based on this nanocomposite material can rapidly, easily, and sensitively detect the concentration of HQ. By utilizing the color change caused by the redox reaction of TMB, quantitative analysis of HQ can be achieved. The concentration of HQ can be determined by naked eye based on the color intensity in just 10 minutes. Furthermore, the concentration of HQ in the solution can be further accurately analyzed using a UV-Vis spectrophotometer. Combining the advantages of visual assessment and instrument detection, it can provide rapid and reliable HQ detection results. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0040] Figure 2 The microstructure diagrams of Co@NC and PAN / PS / ZIF nanofibers of the present invention are as follows: (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 image of Co@NC.

[0041] Figure 3 XRD and Raman plots for NC and Co@NC: (A) XRD plots of NC and Co@NC; (B) Raman plots of NC and Co@NC.

[0042] Figure 4 The oxidation activity of Co@NC and its influencing factors are as follows: (A) UV-Vis spectra of TMB, Co@NC and their mixed solutions; (B) Effect of pH on the oxidation activity of Co@NC; (C) Effect of Co@NC on the oxidation activity of Co@NC; (D) Effect of TMB concentration on the oxidation activity of Co@NC.

[0043] Figure 5 Quantitative detection of HQ for Co@NC: (A) UV-Vis spectra of the Co@NC-TMB system at different HQ concentrations; (B) Linear relationship between absorbance and HQ concentration.

[0044] Figure 6 Comparison of Co@NC and C3N4-ZIF: (A) UV-Vis spectrum of oxidation activity; (B) UV-Vis spectrum after adding HQ. Detailed Implementation

[0045] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0046] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

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

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

[0050] This invention provides a method for preparing transition metal nitrogen-carbon nanocomposite materials, the method comprising:

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

[0052] S2. The mixture is subjected to solid-liquid separation, followed by washing and drying to obtain ZIF-67;

[0053] S3. Polyacrylonitrile and polystyrene are co-dispersed in an organic solvent, and then ZIF-67 is added to obtain a spinning solution;

[0054] S4. Electrospin the spinning solution to obtain a fiber membrane;

[0055] S5. The fiber membrane is pre-oxidized, then calcined, and the calcined product is cooled and ground to obtain the transition metal nitrogen carbon nanocomposite material Co@NC.

[0056] Step S1 specifically includes:

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

[0058] 2-Methylimidazole is dissolved in the mixed solvent to obtain a 2-methylimidazole solution;

[0059] The cobalt nitrate solution and the 2-methylimidazole solution were mixed and reacted for 24±4 h to obtain a mixture.

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

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

[0062] The concentration of cobalt nitrate in the mixture is 0.06–0.08 mol / L.

[0063] Step S2 specifically includes:

[0064] The mixture was subjected to solid-liquid separation. The resulting solid was washed several times with ethanol and then dried at 60±10℃ to obtain ZIF-67.

[0065] Step S3 specifically includes:

[0066] Polyacrylonitrile and polystyrene were co-dispersed in N,N-dimethylformamide, and then ZIF-67 was added. The mixture was stirred for 12±2 h to obtain a spinning solution.

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

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

[0069] In this invention, the mass ratio of polyacrylonitrile, polystyrene, and ZIF-67 in the spinning solution is 2:1:1. The amount of ZIF-67 is moderate. If the ZIF-67 content is too low, there will be fewer active sites of Co after calcination, resulting in low catalytic activity for TMB oxidation. If the ZIF-67 content is too high, active sites are prone to aggregation after calcination, which will prevent the full utilization of its catalytic performance. Polyacrylonitrile and polystyrene both serve to support ZIF-67 and disperse it, preventing MOF agglomeration. Polyacrylonitrile has a high nitrogen content, and polystyrene has stable chemical properties. As a supporting material, it can improve the stability of the composite material.

[0070] Step S4 specifically includes:

[0071] The spinning solution was subjected to electrospinning with a positive spinning voltage of 18kV, a negative spinning voltage of -2kV, and a feeding rate of 1mL / h to obtain a fiber membrane.

[0072] Step S4 specifically includes:

[0073] The fiber membrane was pre-oxidized at 200±20℃ for 1-3 hours, then heated to 500±50℃ at a heating rate of 5±1℃ / min under an inert atmosphere and held for 1-3 hours. It was then heated to 800±50℃ at a heating rate of 1-3℃ / min and calcined for 1-3 hours. After the calcined product cooled naturally, it was ground to obtain the transition metal nitrogen carbon nanocomposite material Co@NC.

[0074] In this invention, the advantage of pre-oxidizing the fiber membrane at 200±20℃ is that it enhances the thermal stability of the fiber. If the unoxidized fiber membrane is directly heated to 800℃, the fiber membrane may melt or stick together due to thermal decomposition, resulting in the destruction of the surface microstructure.

[0075] In this invention, the calcination is carried out in two stages. The purpose of calcining at 500±50℃ for 1 to 3 hours is to remove organic ligands and adsorbed water from the fiber membrane, while simultaneously forming a preliminary carbon skeleton structure. If the temperature is directly heated to 800℃, the rapid gas release may cause the fiber structure to break.

[0076] The advantage of calcining at 800±50℃ for 1 to 3 hours is that it can promote the graphitization process, increase the degree of Co crystallization, and improve the stability of the composite fiber material.

[0077] The following will describe in detail the preparation method of a transition metal nitrogen-carbon nanocomposite material of the present invention and its application in the detection of hydroquinone, with reference to embodiments and experimental data.

[0078] Example 1

[0079] This embodiment provides a method for preparing transition metal nitrogen-carbon nanocomposite materials, as detailed below:

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

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

[0082] PAN / PS nanofibers were prepared using the same method as in step (2), except that ZIF-67 nanoparticles were not added. The resulting product was denoted as NC.

[0083] Comparative Example 1

[0084] This embodiment provides a method for preparing a transition metal nitrogen-carbon composite material, as detailed below:

[0085] 0.291 g of cobalt nitrate hexahydrate was dissolved in 10 mL of methanol, and 0.656 g of 2-methylimidazole was dissolved in 15 mL of methanol. The two solutions were mixed together, and then 0.25 g of C3N4 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.) was added. The mixture was stirred for 24 hours, washed three times with methanol, dried at 60 °C overnight, ground, and then calcined in a tube furnace at a rate of 2 °C per minute to 350 °C and held for 90 min. Then, under an argon atmosphere, the mixture was heated to 600 °C at a rate of 2 °C per minute and held for 2 h. After cooling, C3N4-ZIF was finally obtained.

[0086] Example 2

[0087] This embodiment verifies the HQ detection performance of the product obtained in Example 1.

[0088] "turn-off" colorimetric detection HQ

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

[0090] First, 0.25 mM 3,3,5,5-tetramethylbenzidine (TMB) and Co@NC material were added sequentially to a 0.2 M HAc-NaAc (pH = 3.6) buffer solution, and then incubated at 37 °C for 10 minutes. The absorption peak of the solution at 652 nm was detected by a UV-Vis spectrophotometer.

[0091] (2) Colorimetric detection of HQ concentration

[0092] 0.2M HAc-NaAc, 10μg / mL Co@NC, 1mM TMB and different concentrations of HQ were added sequentially to cuvettes, and then incubated at 37℃ for 10 minutes. The absorption peaks of different solutions at 652nm were recorded to establish a linear relationship between different HQ concentrations and absorbance intensity.

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

[0094] The principle of detecting hydroquinone (HQ) using the transition metal nitrogen-carbon (Co@NC) nanofiber material prepared in Example 1 is as follows: Figure 1As shown in the figure, Co@NC can oxidize colorless 3,3,5,5-tetramethylbenzidine (TMB) into blue oxTMB. This is likely due to the presence of Co on the surface of Co@NC. 3+ and Co 2+ And Co 3+ / Co 2+ A high reduction potential can oxidize TMB, resulting in a strong absorption peak at 652 nm. With the addition of HQ, the blue solution gradually fades because the oxidized oxTMB oxidizes HQ, reducing itself to colorless TMB. Based on the color change caused by different HQ concentrations, rapid, simple, and sensitive analytical detection can be achieved.

[0095] Co@NC is obtained by calcining a blend of zeolite imidazole ester backbone material ZIF-67 with polyacrylonitrile (PAN) and polystyrene (PS), and its morphology is as follows. Figure 2 As shown in Figure (A), ZIF-67 is embedded in PAN / PS nanofibers, forming a unique "jewel chain" structure. Even after pre-oxidation and carbonization, the PAN / PS / ZIF-67 nanofilm retains its fibrous structure. To observe its morphology more clearly, Figure (D) shows a TEM image of Co@NC. It can be seen that the carbonized ZIF-67 internally decomposes into many black Co nanoparticles of varying sizes. The high-resolution TEM image shown in Figures (EF) clearly shows crystal striations, indicating that the material has good crystallinity.

[0096] The crystal structures of NC and Co@NC were analyzed by XRD. Figure 3 As shown in (A), all materials exhibit a broad diffraction peak at approximately 26°, attributed to the (002) plane of graphitic carbon. Co@NC nanofibers show three relatively sharp peaks at 44.2°, 51.5°, and 75.8°, corresponding to the (111), (200), and (220) crystal planes of Co (JCPDS No. 89-4307), indicating the decomposition of the organic ligands in the MOF and the reduction of ZIF-67 to Co nanoparticles during high-temperature calcination. The degree of defect and graphitization of the nanofibers was further investigated using Raman spectroscopy. Figure 3 As can be seen in (B), all samples were at 1340 and 1590 cm⁻¹. -1 The two strong peaks nearby correspond to the D band of defective carbon and the sp band of ordered graphite, respectively. 2 The G-band of carbon. The intensity ratio of the D and G bands (I D / I G This reflects the defects present in the nanofibers and the amount of conductive graphite. D / I GA higher value indicates a higher defect level in the material. Generally, a higher degree of graphitization, i.e., a lower defect level, is beneficial for improving the conductivity of carbon materials. In fact, the electron transfer capability of electrode materials has a significant impact on the performance of electrochemical sensors. The Ic of NC and Co@NC... D / I G The similarity indicates that both have a similar degree of crystallization.

[0097] like Figure 4 (A) Neither TMB nor Co@NC exhibits absorption peaks in the 800-400 nm range, but their mixed solution shows a distinct absorption peak at 652 nm, indicating that Co@NC can directly oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxTMB. This may be due to the Co on the surface of Co@NC. 3+ / Co 2+ The high redox potential of Co@NC leads to the oxidation of TMB in acidic Hac-NaAc solution. The effect of the reaction environment on the oxidation activity of Co@NC was then investigated. As shown in Figure (B), the optimal pH value is 3.6. Furthermore, 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 652nm gradually decreases, such as Figure 5 As shown in (A). Meanwhile... Figure 5 The illustration in (B) shows that the blue color of the solution gradually fades. This is likely because oxTMB, in a highly oxidized state, oxidizes HQ to benzoquinone (BQ), while being reduced to colorless TMB, thus inhibiting the oxidation of TMB and causing the blue color to disappear. Within the range of 0.005–0.1 mM, a good linear relationship exists between absorbance and concentration, with the linear equation 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 As shown in (A) and (B), C3N4-ZIF cannot turn colorless TMB into blue oxTMB. After adding HQ, the color of the mixed solution of Co@NC and TMB becomes lighter, while the color of C3N4-ZIF remains unchanged. Therefore, C3N4-ZIF cannot achieve colorimetric detection of HQ. The above results indicate that the Co@NC of this invention can be used for colorimetric detection of HQ, and this method has not been previously reported. Furthermore, the material exhibits excellent detection performance.

[0100] The ZIF-67 material prepared in this invention, after being calcined at 800℃, forms Co nanoparticles. The principle of catalytic oxidation of colorless TMB to oxTMB is that Co exists on the Co surface.3+ / Co 2+ Due to Co 3+ / Co 2+ It has a high reduction potential, so it can directly oxidize TMB. The ZIF-67 material prepared in Comparative Example 1 was calcined at a relatively low temperature of 500℃, which prevented the formation of Co nanoparticles, and therefore could not undergo a redox reaction with TMB.

[0101] In summary, this invention successfully develops a rapid, simple, and sensitive colorimetric detection method for HQ concentration. Utilizing the color change caused by the TMB redox reaction, quantitative analysis of HQ can be achieved. This method is fast, requiring only 10 minutes, allowing for visual assessment of HQ concentration based on color intensity. Furthermore, it can be further refined using a UV-Vis spectrophotometer for more accurate analysis of HQ concentration in the solution. Combining the advantages of visual assessment and instrumental detection, it provides rapid and reliable results.

[0102] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0103] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0104] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. The application of a transition metal nitrogen-carbon nanocomposite material in the colorimetric detection of hydroquinone, wherein the preparation method of the transition metal nitrogen-carbon nanocomposite material includes: Cobalt nitrate solution and 2-methylimidazole solution were mixed and allowed to react fully to obtain a mixture; The mixture was subjected to solid-liquid separation, followed by washing and drying to obtain ZIF-67; Polyacrylonitrile and polystyrene were co-dispersed in an organic solvent, and then ZIF-67 was added to obtain a spinning solution; The spinning solution is electrospinned to obtain a fiber membrane; The fiber membrane was pre-oxidized, then calcined, and the calcined product was cooled and ground to obtain the transition metal nitrogen carbon nanocomposite material Co@NC; The step of dispersing polyacrylonitrile and polystyrene together in an organic solvent, followed by the addition of ZIF-67 to obtain the spinning solution, specifically includes: Polyacrylonitrile and polystyrene were co-dispersed in N,N-dimethylformamide, and then ZIF-67 was added. The mixture was stirred for 12±2 h to obtain the spinning solution. The mass ratio of polyacrylonitrile, polystyrene and ZIF-67 in the spinning solution is 2:1:4; The concentration of ZIF-67 in the spinning solution is 0.2 g / mL; The process involves pre-oxidizing the fiber membrane, followed by calcination, and then grinding the calcined product after cooling to obtain the transition metal nitrogen-carbon nanocomposite material Co@NC. Specifically, this includes: The fiber membrane was pre-oxidized at 200±20 °C for 1–3 h, then heated to 500±50 °C at a heating rate of 5±1 °C / min under an argon atmosphere and held for 1–3 h. It was then heated to 800±50 °C at a heating rate of 1–3 °C / min and calcined for 1–3 h. After the calcined product cooled naturally, it was ground to obtain the transition metal nitrogen carbon nanocomposite material Co@NC. The colorimetric detection of hydroquinone utilizes the color change caused by the redox reaction of 3,3,5,5-tetramethylbenzidine to achieve the detection of hydroquinone.

2. The application according to claim 1, characterized in that, The process of mixing cobalt nitrate solution and 2-methylimidazole solution and allowing them to react fully to obtain a mixture specifically includes: Cobalt nitrate is dissolved in a mixed solvent of methanol and ethanol to obtain a cobalt nitrate solution; 2-Methylimidazole is dissolved in the mixed solvent to obtain a 2-methylimidazole solution; The cobalt nitrate solution and the 2-methylimidazole solution were mixed and reacted for 24±4 h to obtain a mixture.

3. The application according to claim 2, characterized in that, In the mixed solvent, the volume ratio of methanol to ethanol is 1:1; In the mixture, the molar ratio of cobalt nitrate to 2-methylimidazole is 1:3.9; The concentration of cobalt nitrate in the mixture is 0.06–0.08 mol / L.

4. The application according to claim 1, characterized in that, The process of solid-liquid separation, followed by washing and drying, to obtain ZIF-67 specifically includes: The mixture was subjected to solid-liquid separation. The resulting solid was washed several times with ethanol and then dried at 60±10℃ to obtain ZIF-67.

5. The application according to claim 1, characterized in that, The step of electrospinning the spinning solution to obtain a fiber membrane specifically includes: The spinning solution was subjected to electrospinning with a positive spinning voltage of 18 kV, a negative spinning voltage of −2 kV, and a feeding rate of 1 mL / h to obtain a fiber membrane.

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