Fe3O4-coated CFPDA-coated Pt nano-catalyst and preparation method and application thereof

Abstract

The invention relates to a Fe3O4 (at) CFPDA (at) Pt nano-catalyst, a preparation method thereof and an application of the Fe3O4 (at) CFPDA (at) Pt nano-catalyst in rapid colorimetric detection of hydrogen peroxide, and the Fe3O4 (at) CFPDA (at) Pt nano-catalyst can be obtained by adding F127 / P123 / mesitylene into a water-alcohol dispersion liquid of Fe3O4 to carry out solvothermal reaction, then adding ammonium chloroplatinate, carrying out reduction by sodium borohydride, carrying out magnetic separation on a product and drying the product. The Fe3O4 (at) CFPDA (at) Pt nano-catalyst disclosed by the invention can be used for efficiently detecting H2O2; the Fe3O4-coated CFPDA-coated Pt nano-catalyst has the advantages of high catalytic activity, stability and magnetic recoverability, and can realize rapid detection of H2O2 under the conditions of wide linear range and low detection limit; meanwhile, the problem that the activity-stability-recoverability of a traditional catalyst is difficult to be compatible is solved, and the application scene of portable H2O2 detection is expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation and analysis and detection of nanomaterials, and particularly relates to a Fe3O4@C FPDA @Pt nanocatalyst (FPDA: flower-like polydopamine; @: coating;), a preparation method thereof, and an application in the rapid detection of hydrogen peroxide (H2O2) based on the 3,3',5,5'-tetramethylbenzidine (TMB) colorimetric method. Background Art

[0002] Hydrogen peroxide is an important molecule in biological metabolism and industrial production, and its rapid and sensitive detection is of great significance in environmental monitoring, food safety, and biomedical fields. Traditional detection methods (such as electrochemical methods and chromatographic methods) have disadvantages such as expensive instruments and complex operations, while colorimetric methods have attracted much attention due to advantages such as simple operation, low cost, and visual detection. However, existing colorimetric method catalysts have low catalytic efficiency, poor stability, and complex synthesis processes, which limit their practical applications.

[0003] Fe3O4 nanoparticles are widely used as carrier materials due to their magnetic easy separation characteristics, but their catalytic activity is insufficient when used alone. Coating with a carbon layer can improve their stability, and loading noble metals (such as Pt) can significantly enhance the catalytic performance. At present, how to design nanocatalysts with both high catalytic activity, stability, and magnetic separation performance and realize their application in the rapid detection of H2O2 still requires further breakthroughs. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a core-shell structured Fe3O4@C FPDA @Pt nanocatalyst and a preparation method thereof, to solve the problems of low activity and poor stability of existing catalysts, and to achieve highly sensitive and rapid detection of H2O2 based on the TMB colorimetric method.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a Fe3O4@C FPDA @Pt nanocatalyst, comprising the following steps: 1) Weigh FeCl3·6H2O, dodecylamine, and NH4Ac and place them in an ethylene glycol solvent. After ultrasonic-assisted dissolution, magnetically stir in an oil bath to form a homogeneous precursor solution; transfer the homogeneous precursor solution to a polytetrafluoroethylene high-pressure reaction kettle and perform constant-temperature crystallization in an oven; after the reaction is completed, cool to room temperature, quickly separate the black product, wash it five times alternately with ultrapure water / ethanol to remove residual organic substances, and dry it in vacuum to obtain monodisperse Fe3O4 nanoparticles; 2) Add monodisperse Fe3O4 nanoparticles into a conical flask containing a mixed solution of ethanol and water to form mixture A; add F127 (polyethylene oxide - polypropylene oxide - polyethylene oxide), P123 (polyethylene oxide - polypropylene oxide - polyethylene oxide), and DA·HCl (dopamine hydrochloride) into a round-bottom flask containing a mixed solution of ethanol and water to form a clear solution, then add mesitylene to form an emulsion system to obtain mixed solution B; add mixed solution B into mixture A, stir mechanically, then add ammonia dropwise and continue stirring; collect the precipitate by magnetic separation, and remove P123 and F127 with absolute ethanol and acetone to obtain the Fe3O4@FPDA precursor. 3) Place the Fe3O4@FPDA precursor in a quartz boat of a tubular furnace, purge the air with argon, then increase the temperature programmatically and maintain for a certain time; complete the pyrolysis process of polydopamine under an argon atmosphere, and naturally cool to room temperature to obtain Fe3O4@C FPDA composite material; 4) Uniformly disperse the Fe3O4@C FPDA composite material in deionized water, add ammonium chloroplatinate solution and impregnate by ultrasonic; then, under nitrogen protection, dropwise add freshly prepared NaBH4 reducing agent, and complete the reduction of Pt 4+ ; collect Fe3O4@C FPDA @Pt by magnetic separation, after washing and purification, dry in vacuum to obtain the final product, namely Fe3O4@C FPDA @Pt nanocatalyst.

[0006] Preferably, in step 1), the molar ratio of FeCl3·6H2O, dodecylamine, and NH4Ac is 1:0.9 - 1.2:0.01 - 0.03, the constant-temperature crystallization temperature condition is 200 - 240 °C, and the reaction time is 10 - 30 h.

[0007] Preferably, in step 2), the mass ratio of Fe3O4, F127, P123, and DA·HCl in mixture A is 1∶3 - 5∶1 - 2∶3 - 5, the stirring time is 4 - 12 h; the addition amount of mesitylene in mixed solution B is 2 - 4 mL; the dropping rate of ammonia is 5 - 10 mL / min, and the dropping volume is 2 - 3 mL.

[0008] Preferably, in step 3), the pyrolysis temperature is 400 - 900 °C, and the pyrolysis time is 1.5 - 2.5 h.

[0009] Preferably, in step 4), the mass ratio of ammonium chloroplatinate to the Fe3O4@C FPDA composite material is 0.1 - 0.2∶1, the ultrasonic impregnation time is 0.5 - 1 h, and the constant-temperature stirring time is 3 - 5 h.

[0010] The present invention further provides Fe3O4@C prepared by the preparation method as described above FPDA @Pt nanocatalyst.

[0011] The present invention further provides a method for rapid colorimetric detection of hydrogen peroxide by using Fe3O4@C FPDA @Pt nanocatalyst, comprising the following steps: a) Mix Fe3O4@C FPDA @Pt nanocatalyst (0.01 g / L) with TMB solution (0.416 mM), and add the above mixed solution into a centrifuge tube; b) Add the H2O2 solution to be tested (1 - 2500 μM), and catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate a blue product (TMB ox); c) Measure the absorbance at 652 nm by using an ultraviolet-visible spectrophotometer, and perform semi-quantitative detection through color change; d) The results show that the absorbance of the solution has a linear relationship with the concentration of H2O2 solution (0.195 - 12.5 mM), and quantitative detection can be achieved thereby.

[0012] Nanomaterials such as carbon materials, Fe3O4, and Pt have excellent catalytic performance and can all oxidize TMB to TMB ox in the presence of H2O2. The Fe3O4@C FPDA @Pt nanocatalyst synthesized in the present invention has been proven by experiments to have a good catalytic effect on the decomposition of H2O2 to generate reactive oxygen species and rapidly oxidize TMB to develop color.

[0013] Compared with the prior art, the method of the present invention is simple and efficient. The composite metal oxide, carbon layer and noble metal in the present invention are to combine the advantages of various catalysts. Specifically as follows: 1. Traditional H2O2 colorimetric catalysts (such as pure Fe3O4 or noble metal sols) are difficult to have both high catalytic activity and easy recyclability. In the present invention, the Fe3O4 core endows the material with magnetic separation ability, the carbon layer can effectively prevent the aggregation of Fe3O4 and fix Pt nanoparticles, and the highly dispersed Pt significantly improves the H2O2 decomposition efficiency by exposing active sites on the surface. The three work together to solve the problem that activity-stability-recyclability is difficult to be compatible. 2. The detection limit of the existing TMB colorimetric method based on Fe3O4 or carbon-based catalysts is usually higher than 1 μM. However, with the strong catalytic activity of Pt and the promotion of electron transfer by the carbon layer in the present invention, the concentration of ·OH free radicals generated by the decomposition of H2O2 is doubled, so that the detection limit is reduced to 0.1 μM. 3. Existing methods mostly rely on centrifugal separation or immobilized enzymes, with cumbersome steps and time-consuming. The catalyst of the present invention can be directly separated quickly by a magnet. Combining with the instantaneity of the TMB color reaction, the whole detection process is shortened to 5 minutes, and semi-quantitative visual interpretation can be realized without professional equipment, which is especially suitable for on-site detection scenarios with limited resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0015] Figure 1 TEM image of the Fe3O4@C FPDA composite material prepared in Example 1.

[0016] Figure 2 For the Fe3O4@C FPDA @Pt nanocatalyst prepared in Example 1.

[0017] Figure 3 For the Fe3O4@C FPDA XRD pattern of the @Pt nanocatalyst prepared in Example 1.

[0018] Figure 4 Graph of the absorbance of the reaction solution at 652 nm versus the concentration of H2O2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0020] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Example 1: A preparation method of Fe3O4@C FPDA @Pt nanocatalyst is as follows: (1) Dissolve 0.01 mol of FeCl3·6H2O, 0.01 mol of dodecylamine, and 0.2 mmol of NH4Ac completely in 100 mL of ethylene glycol to prepare a solution; (2) Transfer the solution to a high-pressure reaction kettle and react at 230 °C for 30 h; (3) After the solution is cooled to room temperature, collect the product by magnetic separation, wash it three times alternately with ultrapure water and absolute ethanol, and then dry it in vacuum at 80 °C for 12 h to obtain monodisperse Fe3O4 nanoparticles; (4) Add 100 mg of monodisperse Fe3O4 nanoparticles to a conical flask containing a mixed solution of ethanol and water to form mixture A; disperse 300 mg of F127, 150 mg of P123, and 500 mg of DA·HCl in ethanol / water (V∶V = 1∶1), stir for 1 h until evenly dispersed, then add 3 mL of mesitylene to prepare dispersion B; add dispersion B to mixture A, continue mechanical stirring for 10 min, then add 2.5 mL of ammonia water and continue stirring for 5 h; collect the precipitate by magnetic separation, wash it with a mixed solution of absolute ethanol and acetone to remove the excess P123 / F127, and obtain the Fe3O4@FPDA precursor; (5) Place the Fe3O4@FPDA precursor in a tube furnace under an inert atmosphere and pyrolyze it at 900 °C for 2 h to obtain Fe3O4@C FPDA composite material; (6) Disperse the Fe3O4@C FPDA composite material and ammonium chloroplatinate in a mass ratio of 1∶0.1 in 30 mL of ultrapure water, ultrasonicate for 1 h, then add 6 mg of sodium borohydride, react for 3 h, collect the precipitate by magnetic separation, wash it three times in sequence with ultrapure water and absolute ethanol, and then dry it in vacuum at 80 °C for 12 h to obtain Fe3O4@C FPDA @Pt nanocatalyst.

[0022] From Figures 1 to 3 it can be seen that Fe3O4@C FPDA @Pt nanocatalyst was successfully prepared. Figure 1 In the TEM image of FPDA it can be clearly seen that there are wrinkled substances wrapping the Fe3O4 core, indicating that C Figure 2 was successfully wrapped on the surface of Fe3O4; FPDA In the TEM image of Figure 3 it can be clearly seen that there are black nanoparticles on the surface of the wrinkled carbon material, indicating the successful preparation of the Fe3O4@C FPDA @Pt nanocatalyst.

[0023] Figure 4 is the graph of the absorbance of the reaction solution at 652 nm versus the change in H2O2 concentration. The absorbance increases sharply as the H2O2 concentration increases from 0.1 μM to 12.5 mM, and its increasing trend slows down above 195 μM. The absorbance of TMB ox and the H2O2 concentration show a linear relationship in the range of 0.1 to 195 μM ( R 2 = 0.9976), enabling quantitative detection, and the limit of detection (LOD) is calculated to be 0.1 μM.

[0024] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the examples shown and described herein.

Claims

1. A preparation method of Fe3O4@C FPDA @Pt nanocatalyst, characterized in that It includes the following steps: 1) Weigh FeCl3·6H2O, dodecylamine and NH4Ac and place them in an ethylene glycol solvent. After ultrasonic-assisted dissolution, magnetically stir in an oil bath to form a homogeneous precursor solution; transfer the homogeneous precursor solution to a polytetrafluoroethylene high-pressure reaction kettle, carry out constant-temperature crystallization in an oven. After the reaction is completed, cool to room temperature, quickly separate the black product, wash it alternately with ultrapure water / ethanol to remove residual organic matter, and then vacuum dry to obtain monodisperse Fe3O4 nanoparticles; 2) Add the monodisperse Fe3O4 nanoparticles to a conical flask containing a mixed solution of ethanol and water to form mixture A; add F127, P123, DA·HCl to a round-bottom flask containing a mixed solution of ethanol and water to form a clear solution, and then add mesitylene to form an emulsion system to obtain mixed solution B; add the mixed solution B to the mixture A, after mechanical stirring, add ammonia water dropwise and then continue stirring; magnetically separate and collect the precipitate, and remove P123 and F127 with absolute ethanol and acetone to obtain the Fe3O4@FPDA precursor; 3) Place the Fe3O4@FPDA precursor in a quartz boat of a tube furnace. After purging the air with argon, raise the temperature and complete the pyrolysis process of polydopamine under an argon atmosphere. After natural cooling to room temperature, obtain Fe3O4@C coated with a graphitized carbon layer FPDA composite material; 4) Disperse the Fe3O4@C FPDA composite material uniformly in deionized water, add ammonium chloroplatinate solution and impregnate it by ultrasonic wave. Subsequently, under the protection of nitrogen, dropwise add NaBH4 reducing agent, and complete the reduction of Pt 4+ after constant temperature stirring; Collect Fe3O4@C FPDA @Pt by magnetic separation, after washing and purification, obtain the Fe3O4@C FPDA @Pt nanocatalyst after vacuum drying.

2. The preparation method of the Fe3O4@C FPDA @Pt nanocatalyst as claimed in claim 1, characterized in that In step 1), the molar ratio of FeCl3·6H2O, dodecylamine and NH4Ac is 1∶0.9~1.2∶0.01~0.03, the constant-temperature crystallization temperature is 200~240 °C, and the reaction time is 10~30 h.

3. The preparation method of the Fe3O4@C FPDA @Pt nanocatalyst, characterized in that In step 2), the mass ratio of Fe3O4, F127, P123 and DA·HCl in mixture A is 1∶3~5∶1~2∶3~5, and the stirring time is 4~12 h; the addition amount of mesitylene in mixed solution B is 2~4 mL; the dropping rate of ammonia water is 5~10 mL / min, and the dropping volume is 2~3 mL.

4. The preparation method of the Fe3O4@C FPDA @Pt nanocatalyst as claimed in claim 1, characterized in that In step 3), the pyrolysis temperature is 400~900 °C, and the pyrolysis time is 1.5~2.5 h.

5. The preparation method of the Fe3O4@C FPDA @Pt nanocatalyst, characterized in that In the step 4), the mass ratio of ammonium chloroplatinate to the Fe3O4@C FPDA composite material is 0.1-0.2:1, the ultrasonic impregnation time is 0.5-1 h, and the constant temperature stirring time is 3-5 h.

6. An Fe3O4@C FPDA @Pt nanocatalyst prepared by the preparation method described in any one of claims 1-5.

7. Application of the Fe3O4@C FPDA @Pt nanocatalyst as claimed in claim 6 in rapid colorimetric detection of hydrogen peroxide.

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