Preparation method, product and application of an iron monatomic catalyst

Abstract

The present application relates to iron monatomic catalyst and ClO ‑ The present application relates to the technical field of detection, and particularly relates to a preparation method of an iron monatomic catalyst, a product and application.The preparation method of the iron monatomic catalyst comprises the following steps: uniformly mixing melamine, L-alanine and an iron salt, and then calcining to obtain the iron monatomic catalyst.The iron monatomic catalyst prepared by the method can monitor ClO- in real time, has a good linear response to ClO- in a range of 5.16*10 ‑5 4 M to 0.0253*10 ‑ 4 M, and can successfully detect ClO- contained in liquid (wastewater).

Description

Technical Field

[0001] This invention relates to iron single-atom catalysts and ClO in water samples. - The field of detection technology, particularly, relates to a method for preparing an iron single-atom catalyst, its products, and their applications. Background Technology

[0002] Chlorine-containing disinfectants are very common and widely used in the market, typically applied to medical wastewater, drinking water, swimming pool water, etc. Extensive use has led to the accumulation of hypochlorite ions, which can be very harmful to human health. Furthermore, sodium hypochlorite is an effective oxidant and disinfectant. First, hypochlorous acid further decomposes to form nascent oxygen [O]. The extremely strong oxidizing properties of nascent oxygen denature the proteins of bacteria and viruses, thus killing pathogenic microorganisms. Second, in the process of sterilization and virucidal activity, hypochlorous acid not only acts on cell walls and viral capsids, but also, due to its small size and lack of charge, it can penetrate into the bacteria (viruses) and react with their proteins, nucleic acids, and enzymes to oxidize them or destroy their phosphate dehydrogenases, causing metabolic disorders and cell death, thereby killing pathogenic microorganisms. Simultaneously, the chloride ions produced by hypochlorous acid can significantly alter the osmotic pressure of bacteria and viruses, causing their cells to lose activity and die.

[0003] Currently, we have many methods for detecting hypochlorite, such as fluorescence, chemiluminescence, and spectrophotometry. However, these methods still have some limitations. Firstly, their selectivity is not high; secondly, they cannot achieve in-situ detection; thirdly, the detection cost is too high; and fourthly, the portability of the detection instruments is limited or nonexistent. Electrochemical methods, based on reduction and oxidation reactions, are characterized by simple operation, excellent performance, easy miniaturization of equipment, and high sensitivity.

[0004] The key to constructing efficient and ultrasensitive sensors lies in the design and synthesis of electrochemical sensing active materials. In recent years, single-atom catalysts with a single metal atom as the active center have attracted widespread attention. Iron single-atom catalysts, based on the redox reaction between Fe(II) and Fe(III), have exhibited excellent catalytic performance, possessing high efficiency, high selectivity, and high stability. However, the sensitivity of current iron single-atom catalysts in detecting ClO- in wastewater needs further improvement. Summary of the Invention

[0005] Based on the above, this invention provides a method for preparing an iron single-atom catalyst, a product, and its application. The iron single-atom catalyst of this invention can be fabricated into a flexible chip that enables real-time monitoring of ClO-, and at a wavelength of 5.16 × 10⁻⁶. -5 It exhibits a good linear response to ClO- in the range of μM to 0.0253 μM.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of the present invention is a method for preparing an iron single-atom catalyst, comprising the following steps: mixing melamine, L-alanine and iron salt evenly, and then calcining to obtain the iron single-atom catalyst.

[0008] The second technical solution of the present invention is an iron single-atom catalyst prepared according to the above preparation method.

[0009] The third technical solution of this invention is the application of the above-mentioned iron single-atom catalyst in the construction of electrochemical sensing active materials.

[0010] The fourth technical solution of the present invention is a method for preparing an iron single-atom-based flexible sensing chip, comprising the following steps: preparing the above-mentioned iron single-atom catalyst into a conductive ink, and constructing the iron single-atom-based flexible sensing chip using high-resolution electrohydrodynamics (EHD) jet technology.

[0011] The fifth technical solution of the present invention is an iron single-atom-based flexible sensing chip prepared according to the above-described preparation method.

[0012] The sixth technical solution of this invention is that the above-mentioned iron single-atom-based flexible sensing chip can detect ClO in water samples. - Application of content.

[0013] The present invention discloses the following technical effects:

[0014] The preparation method of this invention is simple and easy to carry out on a large scale for industrial production.

[0015] The iron single-atom catalyst prepared using the method of this invention can monitor ClO in real time. - And at 5.16×10 -5 It exhibits a good linear response to ClO- in the range of μM to 0.0253 μM, and can successfully detect ClO- in various water samples. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a process flow diagram for the preparation of the iron single-atom catalyst of the present invention.

[0018] Figure 2 The images shown are SEM (a), TEM (b), and aberration-corrected transmission electron microscopy (C) images of the iron single-atom catalyst (Fe / GO SAC) prepared in step 1 of Example 1.

[0019] Figure 3 XRD patterns of Fe / GO SAC and graphene.

[0020] Figure 4 X-ray photoelectron spectroscopy (XPS) characterization of Fe / GO SAC prepared in step 1 of Example 1; wherein, (a) is the complete XPS spectrum of Fe / GO SAC, (b) is the XPS spectrum of C1s, and (c) is the XPS spectrum of Fe 2p.

[0021] Figure 5 The Fe / GO SAC sensor and graphene sensor prepared in Example 1 are for 2.58 nM ClO - The CV response current (a) of the Fe / GO SAC sensor for different concentrations of ClO under the same pH and test potential conditions. - Cyclic voltammetry (CV) response image (b), pH test conditions (c) and optimized applied potential test conditions (d) for the Fe / GO SAC sensor response to ClO-.

[0022] Figure 6 The Fe / GO SAC sensor prepared in Example 1 was subjected to continuous addition of a series of concentrations of ClO at a voltage of -0.30V. - The electrochemical It curve at time (a), the corresponding linear calibration plot of the Fe / GO SAC sensor (b), the repeatability test of Fe / GO SAC sensors prepared in different batches (c), and the anti-interference performance test of the Fe / GO SAC sensor (d).

[0023] Figure 7 The results of the Fe / GO SAC sensor prepared in Example 1 on the concentration of ClO- in various actual wastewaters are shown; (a) is cell culture waste liquid, (b) is dormitory water, (c) is swimming pool water, and (d) is laboratory water. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] Unless otherwise specified, "room temperature" in this invention refers to 20-30°C.

[0030] One of the technical solutions of the present invention is a method for preparing an iron single-atom catalyst, comprising the following steps: mixing melamine, L-alanine and iron salt evenly, and then calcining to obtain the iron single-atom catalyst.

[0031] This invention relates to a method for preparing an iron single-atom catalyst, wherein the target iron single-atom catalyst is obtained by mixing melamine, L-alanine, and an iron salt and then calcining the mixture. Compared with chitosan, melamine has the advantages of high reactivity and low cost; replacing melamine with chitosan in this invention will affect the catalyst's performance. Similarly, L-alanine has the advantages of chiral structure and stability compared to glutamic acid; replacing L-alanine with glutamic acid will cause changes in the stereochemical properties of the catalyst.

[0032] In a preferred embodiment of the invention, the mass ratio of melamine, L-alanine, and iron salt is 60-100:10-15:1. Under these ratio ranges, a C-N complex can be formed first, and it is also beneficial for Fe to be anchored to the substrate material as individual atoms by N. The amount of iron salt used is crucial; increasing the amount of iron salt may lead to the formation of iron oxides or metals, rather than a single-atom state.

[0033] In a preferred embodiment of the present invention, the iron salt is iron acetate tetrahydrate.

[0034] In a preferred embodiment of the present invention, the method of achieving uniform mixing is ball milling.

[0035] In a preferred embodiment of the present invention, the calcination temperature is 700-900°C, the heating rate is 5°C / min, and the time is 2 hours.

[0036] The second technical solution of the present invention is an iron single-atom catalyst prepared according to the above preparation method.

[0037] The third technical solution of this invention is the application of the above-mentioned iron single-atom catalyst in the construction of electrochemical sensing active materials.

[0038] The fourth technical solution of the present invention is a method for preparing a flexible sensing chip based on iron single atoms, comprising the following steps: preparing the above-mentioned iron single atom catalyst into a conductive ink with a viscosity of 14000-18000cp, using a flexible material as a substrate, and constructing the flexible sensing chip based on iron single atoms using high-resolution electrohydrodynamics EHD jet technology.

[0039] In a preferred embodiment of the present invention, a conductive ink with a viscosity of 14,000 to 18,000 cp is prepared by adding an iron single-atom catalyst to a carbon slurry.

[0040] In a preferred embodiment of the present invention, the construction of the iron single-atom-based flexible sensor chip using high-resolution electrohydrodynamic (EHD) jet technology specifically involves: using PET material as the substrate of an EHD printer; using a needle driven by electricity to jet the conductive ink, with the needle distance from the substrate approximately 1 mm; the jetting pressure range being 20-80 kPa; selecting DC mode; and setting the bias voltage to approximately 100 V. Specific printing parameters need to be adjusted in real time according to the printing situation. The jetted electrodes need to be vacuum-dried overnight at 40°C to obtain the iron single-atom-based flexible sensor chip. If the parameter settings are inappropriate, the ink may fail to be printed, or intermittent printing may occur.

[0041] The fifth technical solution of the present invention is an iron single-atom-based flexible sensing chip prepared according to the above-described preparation method.

[0042] The sixth technical solution of this invention is the application of the above-mentioned iron single-atom-based flexible sensor chip in detecting the hypochlorite content in water samples.

[0043] Unless otherwise specified, all raw materials used in the embodiments of this invention can be obtained through commercial channels.

[0044] The experimental instruments and reagents involved in the following embodiments of the present invention are: CHI660E electrochemical analysis system (Shanghai Chenhua Instrument Co., Ltd.); scanning electron microscope (SEM, S-4800, Hitachi, Japan); NaClO solution (Aladdin Company); water is double-distilled water; PBS solution (pH 7.0).

[0045] Unless otherwise specified, all experiments in the following embodiments of the present invention were performed at room temperature.

[0046] The process flow diagram for preparing the iron single-atom catalyst of this invention is shown below. Figure 1 As shown.

[0047] Example 1

[0048] Step 1: Melamine (C3H6N6) (3.6g), L-alanine (C3H7NO2) (0.8g) and iron acetate tetrahydrate (Fe(CH3COO)2·4H2O) (0.06g) were ball-milled and mixed evenly, and then calcined at high temperature (heated to 800℃ at a rate of 5℃ / min and held for 2h) to obtain iron single-atom catalyst (Fe / GO SAC).

[0049] Step 2: Add Fe / GO SAC to the carbon paste at a ratio of 1:400 and mix thoroughly to obtain conductive ink. Use flexible PET material as the substrate on an EHD printer. Using a needle driven by electricity, spray the conductive ink, with the needle distance from the substrate approximately 1 mm. The spraying pressure range is 20-80 kPa, DC mode is selected, and the bias voltage is set to approximately 100 V. After spraying, the electrode is dried overnight at 40°C under vacuum conditions to obtain the Fe / GO SAC sensor (abbreviated as:

[0050] (Flexible chip)

[0051] Figure 2 The images show SEM (a), TEM (b), and aberration-corrected transmission electron microscopy (C) images of the iron single-atom catalyst (Fe / GO SAC) prepared in step 1 of Example 1. Figure 2 As can be seen in (a), the iron single-atom catalyst exhibits a two-dimensional layered structure, as shown in the transmission electron microscope (TEM) image of Fe / GO SAC. Figure 2(b) also shows that Fe / GO SAC exhibits a complete, ultrathin, sheet-like graphene-like structure. Furthermore, images of the Fe / GO SAC material obtained using aberration-corrected transmission electron microscopy (HAADF-STEM) are also shown. Figure 2 In (c), there are high-density bright spots because the mass of Fe atoms is greater than that of C atoms, proving the existence of Fe single atoms.

[0052] Figure 3 XRD patterns of Fe / GO SAC and graphene. Figure 3 Graphene (black curve) exhibits diffraction peaks at 2θ of 26.1° and 44.1°, which are amorphous peaks of carbon. The Fe / GO SAC material shows similar diffraction peaks to GO, with no characteristic crystalline peaks observed, indicating that it, like graphene, is primarily in an amorphous state, further proving that Fe exists in the material as a single atom.

[0053] Figure 4 X-ray photoelectron spectroscopy (XPS) characterization of the Fe / GO SAC prepared in step 1 of Example 1; where (a) is the full scan spectrum of Fe / GO SAC, (b) is the XPS spectrum of C1s, and (c) is the XPS spectrum of Fe 2p. XPS analysis was used to explore the surface chemical state of the catalyst. Figure 4 Image (a) shows that the prepared Fe / GO SAC material mainly contains Fe and C elements. C 1s spectrum ( Figure 4 Image (b) shows the C=O bond (288.90 eV), CO bond (285.60 eV), and C=C bond (284.80 eV) in the carbon skeleton. Figure 4 In (c), 710.50 eV and 722.20 eV correspond to the binding energies of Fe 2p 3 / 2 and Fe 2p1 / 2, respectively.

[0054] Figure 5 (a) shows the Fe / GO SAC sensor (corresponding to FeGO in the figure) and graphene sensor prepared in Example 1 for 2.58 nM ClO - CV response plot of Fe / GO SAC sensor for ClO - The electrochemical catalytic response of the Fe single-atom material was much greater than that of GO, demonstrating that the prepared Fe single-atom material possesses extremely strong catalytic performance. Furthermore, under the same pH and test potential conditions, a series of concentrations of ClO were added to the test substrate. - Subsequently, the CV response of the Fe / GO SAC sensor increased with the change in ClO₂ - The concentration gradually increases, indicating that the constructed sensor exhibits good detection performance for ClO-, such as... Figure 5(b) To investigate the effect of pH on the detection performance of ClO-, CV was used to study the effect of the Fe / GO SAC sensor on ClO- at different pH values. - The electrochemical response behavior of the Fe / GO SAC sensor is shown in Figure 5(c). The results indicate that the Fe / GO SAC sensor exhibits good electrochemical response to ClO₂. - The current response reached its maximum at pH = 7.0. The effect of the applied potential on the detection response of the Fe / GO SAC sensor for NaClO was further investigated, and current-time curves (It) were measured under different voltage conditions. Figure 5 Image (d) shows the reaction of ClO at the same concentration (4.3 nm) under continuous stirring. - Ampere-It curves were obtained by continuously adding the sample to 0.01 mol / L PBS (pH 7.0) at different applied voltages. The current response reached its maximum at -0.30 V. Therefore, the optimal applied potential was -0.30 V. Consequently, pH 7.0 and an operating potential of -0.30 V were selected for subsequent experiments.

[0055] Depend on Figure 6 As shown in (a), the Fe / GO SAC sensor can detect ClO - Real-time monitoring was performed by continuously adding a series of concentrations of ClO2 to the test substrate at -0.30V. - At that time, the sensor's current exhibits a step-like response; Figure 6 (b) shows the Fe / GO SAC sensor printed under optimal conditions for ClO₂. - The linear calibration curve of the response. The calibration curve is at 5.16 × 10⁻⁶. -5 For ClO in the range of μM-0.0253μM - It exhibits good linear response. The linear equation is I(mA) = -6490.74C(ClO) - μM)-3.73649e -5 (R 2 =0.992). These results demonstrate that the Fe / GO SAC sensor can successfully detect ClO in water samples. - Furthermore, flexible sensor chips prepared in different batches exhibit good batch-to-batch reproducibility, such as... Figure 6 As shown in (c). This invention further explores the selectivity of constructing flexible chips, for substances commonly found in water, such as Na+. + Ascorbic acid (AA), uric acid (UA), K + Glucose (Glu) and other substances do not affect ClO - The response caused significant disruption.

[0056] Figure 7The Fe single-atom sensor prepared in Example 1 was used to test ClO in (a) cell waste fluid, (b) dormitory water, (c) swimming pool water, and (d) laboratory water. - The concentration detection results. Based on... Figure 6 The linear equations obtained in the process were used to calculate the ClO in cell waste fluid, dormitory water, swimming pool water, and laboratory water. - The concentrations were 7.77 × 10⁻⁶. -4 μM, 5.50×10 -4 μM, 8.75×10 -5 μM, 3.23×10 -4 μM. The above results indicate that the Fe single-atom sensor has satisfactory potential for the quantitative detection of ClO- in different liquids.

[0057] The Fe single-atom sensor fabricated using the flexible chip from Example 1 was measured five times in sodium hypochlorite at the same concentration, with a relative standard deviation of 3.94%. After the experiment, the sensor was stored at room temperature and then re-detected at different time intervals. In the first three days, the response current returned to 89.6% of its original value. After two weeks and one month of storage, the response current returned to 88.3% and 84.9% of its original value, respectively. This indicates that the Fe single-atom sensor exhibits good reproducibility and stability.

[0058] Comparative Example 1

[0059] The only difference from Example 1 is that step 1 is omitted, and the Fe / GO SAC in step 2 is replaced with iron single-atom fluorescent carbon dot nanozyme powder; the preparation method of this iron single-atom fluorescent carbon dot nanozyme powder is as follows:

[0060] Step S1: Dissolve 0.1g of chitosan in 10mL of 1% (v / v) acetic acid aqueous solution, sonicate in an ultrasonic cleaner for 30min, then add 0.05g of ferrous sulfate heptahydrate and 0.05g of glutamic acid, stir thoroughly to dissolve the solid powder, then add 100μL of ethylenediamine and transfer to a high-temperature reactor, seal and keep at 180℃ for 6h.

[0061] Step S2: After cooling the reaction vessel after step S1 to room temperature, take out the black liquid obtained from the reaction and centrifuge it to remove solid impurities. Then dialyze it with a dialysis bag (MW=500-1000) for 12 hours. Collect the liquid in the dialysis bag and freeze-dry it into a brownish-black powder, which is the iron single-atom fluorescent carbon dot nanozyme powder.

[0062] The flexible chip prepared in this comparative example was subjected to the same effect verification as in Example 1. The results showed that it had a good linear response to ClO- in the range of 0.002 μM-0.015 μM.

[0063] This invention prepares an iron single-atom catalyst and optimizes its structure. The physical properties of the iron single-atom catalyst are characterized using SEM, TEM, and aberration-corrected electron microscopy. The sensing performance of the iron single-atom catalyst for ClO- is studied using electrochemical methods. High-resolution DC solid-state printing technology is used to prepare the iron single-atom catalyst into conductive ink. Using PET as a flexible substrate, the printing process and parameters are continuously optimized to fabricate an iron single-atom-based flexible sensing chip. Laboratory water and factory medical wastewater are used as actual samples for research to test the residual ClO- in the water. - content.

[0064] The iron single-atom catalyst (Fe / GO SAC) prepared using this invention can be used to develop a fully integrated nanoelectronic device, and an electrochemical sensor based on Fe / GO SAC can be constructed using high-resolution electrohydrodynamic (EHD) jet technology. Furthermore, it can be developed into a portable wireless electronic device for transducing and processing electrochemical signals, and then wirelessly outputting them via Bluetooth for various tests.

[0065] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A flexible sensing chip based on iron single atoms for detecting ClO in water samples - Its application in content is characterized by, The method for preparing the iron single-atom-based flexible sensing chip includes the following steps: preparing an iron single-atom catalyst into a conductive ink with a viscosity of 14000~18000cp, using a flexible material as a substrate, and constructing the iron single-atom-based flexible sensing chip using high-resolution electrohydrodynamics EHD jet technology. The preparation steps of the iron single-atom catalyst are as follows: melamine, L-alanine and iron salt are mixed evenly and then calcined to obtain the iron single-atom catalyst; The mass ratio of melamine, L-alanine and iron salt is 60~100:10~15:1; The iron salt is ferric acetate tetrahydrate; The calcination temperature is 700~900℃, the heating rate is 5℃ / min, and the time is 2h.

2. The application according to claim 1, characterized in that, The method for achieving uniform mixing is ball milling.

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