Iodine atom-doped catalyst, method for preparing the same, and use thereof

Abstract

The application discloses an iodine atom doped catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. The application successfully forms an atom-dispersed FeN5 active center on a nitrogen-doped carbon with defects through a heat treatment strategy, simulates natural hematin in structural composition, and simulates the electronic communication effect of a natural enzyme through I doping, and shows excellent catalytic activity on biological small molecules in the human body.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and particularly relates to an iodine atom-doped catalyst, its preparation method, and its application. Background Technology

[0002] Dopamine (DA) is an important catecholamine neurotransmitter in the central nervous system. Abnormal dopamine levels can lead to tachycardia, hypertension, Alzheimer's disease, and depression. Therefore, accurate detection of dopamine is crucial for understanding its biological functions and mechanisms of action, enabling early disease detection and treatment. However, the catalytic oxidation of dopamine involves multiple electron transfer steps, which inherently results in a slow kinetic process, severely hindering research progress. Previous studies have shown that enhancing the adsorption of OH intermediates is key to improving the catalytic activity of dopamine. Recent research indicates that M-Nx single-atom catalysts (SACs) with unfilled and delocalized orbitals are suitable for precisely tuning the interaction between the metal and the adsorbed intermediate, thereby achieving advanced catalytic performance. Inspired by the high activity of natural enzymes, designing M-NxSACs that mimic the structure of heme to capture and activate oxygen-containing intermediates is a feasible approach to further improve catalytic activity. The three-dimensional catalytic pocket formed between the FeN4 site in heme and the axial amino acid ligand establishes good electron communication, thus exhibiting high catalytic performance. Furthermore, it was found that Fe-N5SAC, with its similar three-dimensional structure, exhibits a certain efficiency in catalyzing the oxidation of DA. Unfortunately, the generation of OH during the catalytic process involves the dissociation of water, resulting in the production of H+. + It is possible that protonation of the N atom in the active center could lead to the dissolution of Fe in the active site, thereby compromising the catalyst's stability. Heteroatomic doping can modulate the electronic structure of the active center, which may be a feasible strategy to improve catalytic activity and stability. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention proposes an iodine atom-doped catalyst, its preparation method, and its applications. This invention successfully forms atomically dispersed FeN5 active centers on defective nitrogen-doped carbon through a heat treatment strategy, mimicking the structure and composition of natural heme. Furthermore, by using iodine (I) doping to simulate the electronic communication effect of natural enzymes, it exhibits excellent catalytic activity for human small molecule organisms.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] An iodine atom-doped catalyst, wherein iodine is doped into FeN5 having active centers.

[0006] I doping induces the delocalization of iron 3d electrons and spin transition of iron(II) ions. Furthermore, the introduction of I not only enhances the stability of active sites but also modulates the d-band center of Fe, strengthens the adsorption strength of Fe atomic sites for intermediate OH, and lowers the energy barrier for the oxidation process of small biomolecules.

[0007] This invention also provides a method for preparing the iodine atom-doped catalyst, comprising the following steps: using zinc chloride, ferrous chloride, glucosamine hydrochloride, dicyandiamide, silicon dioxide, and potassium iodide as raw materials, and deionized water as solvent, annealing is performed under a nitrogen atmosphere; the obtained black powder is etched with hydrofluoric acid, and after centrifugation, washing, and drying, the iodine atom-doped catalyst (I / Fe) is obtained. SA NC).

[0008] In this invention, glucosamine hydrochloride and dicyandiamide are used as nitrogen sources, potassium iodide is used as an iodine source, silicon dioxide is used as a template, and zinc chloride volatilizes at high temperatures to form a porous structure.

[0009] Further, the ratio of zinc chloride, ferrous chloride, glucosamine hydrochloride, dicyandiamide, silicon dioxide, and potassium iodide is 0.334 g : 0.15 g : 2.5 g : 2.5 g : 5 mL : (0.1-0.4) g. The preferred mass of potassium iodide is 0.1 g, 0.3 g, and 0.4 g.

[0010] Furthermore, the annealing parameters are: heating rate 5℃ / min, temperature 900℃, and holding time 2h.

[0011] Furthermore, the mass concentration of the hydrofluoric acid is 10%; the etching time is 24 hours.

[0012] The present invention also provides an application of the iodine atom-doped catalyst described above in the preparation of electrode materials, wherein the iodine atom-doped catalyst is dispersed in a solvent to obtain an ink with a concentration of 1 mg / mL, the ink is dropped onto the electrode material, and dried to form a film.

[0013] Furthermore, the solvent is a mixture of water, ethanol, and a 5% (w / w) perfluorosulfonic acid polymer solution in a volume ratio of 50:49:1.

[0014] The present invention also provides an application of the iodine atom-doped catalyst in a sensor.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects:

[0016] This invention synthesizes an iodine-doped FeN5 site catalyst. Iodine forms a stable complex with the N atoms of the adjacent nitrogen-doped carbon layer, mimicking the geometry of axial ligands in heme. The iodine doping establishes an electron communication relationship with the FeN5 sites, which is the reason for its high catalytic activity. Density functional theory (DFT) calculations and experimental studies clearly show that iodine doping enhances the electron delocalization and spin state transition of iron(II), enabling d... z 2 More electrons can readily transition to the 2p orbitals of O, thus promoting the adsorption of the OH intermediate. Furthermore, iodine doping weakens the protonation of active sites and inhibits iron dissolution, thereby improving catalyst stability. This invention provides a rational method for understanding the design and conformational relationships of SACs, and also deepens the understanding of DA oxidation catalysis and how iodine doping modulates its properties. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 Preparation of I / Fe for embodiments of the present invention SA A schematic diagram of NC synthesis;

[0019] Figure 2 From top to bottom, the images show the I / Fe prepared in Example 1, Comparative Example 1, Example 2, and Example 3 of this invention. SA Transmission electron microscopy (TEM) images of NC;

[0020] Figure 3 I prepared in Example 1 of the present invention 0.3 / Fe SA HRTEM image of NC;

[0021] Figure 4 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA AC-HADDF-STEM image of NC;

[0022] Figure 5 I prepared in Example 1 of the present invention 0.3 / Fe SA NC elemental spectrum image;

[0023] Figure 6 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SAX-ray diffraction (XRD) pattern of NC;

[0024] Figure 7 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SA Raman spectra of NC;

[0025] Figure 8 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Adsorption-desorption isotherms and pore size distribution of NC in N2, where a is the adsorption-desorption isotherm and b is the pore size distribution;

[0026] Figure 9 The diagram shows the structure and catalytic mechanism of I / FeSANC and natural heme prepared in this invention;

[0027] Figure 10 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA X-ray photoelectron spectroscopy (XPS) spectrum of NC;

[0028] Figure 11 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA High-resolution XPS I 3d spectrum of NC;

[0029] Figure 12 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA High-resolution XPS Fe2p spectrum of NC;

[0030] Figure 13 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA High-resolution XPSC1s spectrum of NC;

[0031] Figure 14 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SA High-resolution XPS N 1s spectrum of NC;

[0032] Figure 15 I prepared in Example 1 of the present invention 0.3 / FeSA NC and reference sample (Fe) SA Fe-K edge XANES spectra compared to NC, Fe foil, FeO, Fe2O3 and FePc;

[0033] Figure 16 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA The first derivative curves of the Fe-K edge XANES for NC, Fe foil, FeO and Fe2O3;

[0034] Figure 17 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA EXAFS fitting curves for NC, Fe foil, and FePc in R space;

[0035] Figure 18 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA NC) EXAFS Fourier Transform (EXAFS-FT) curve;

[0036] Figure 19 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference samples (Fe foil, FePc and Fe) SA FeK edge EXAFS-WT graph of NC;

[0037] Figure 20 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA NC's amplified UPS spectrum;

[0038] Figure 21 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA χm and 1 / χm plots for NC;

[0039] Figure 22 Schematic diagram of DA oxidation;

[0040] Figure 23 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Cyclic voltammetry curves of NC;

[0041] Figure 24 [Fe(CN)6] 3- / 4- I prepared in solution in Example 1 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Electrochemical impedance spectroscopy (EIS) of NC;

[0042] Figure 25 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Linear sweep frequency voltammetry (LSV) curve of NC;

[0043] Figure 26 Fe with or without DA in PBS (0.1M pH=7.4) SA NC and I 0.3 / Fe SA CV curve of NC;

[0044] Figure 27 Fe with or without DA in PBS (0.1M pH=7.4) SA NC and I 0.3 / Fe SA NC's DPV response;

[0045] Figure 28 The I / Fe prepared in Examples 1, 3 and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SA Sensitivity of NC to oxidation of 100M DA;

[0046] Figure 29 I prepared in Example 1 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The amperometric reaction of NC to DA;

[0047] Figure 30 I prepared in Example 1 at different scan rates (10-250 mV / s) 0.3 / Fe SA Fe prepared by NC (left) and Comparative Example 1 SA CV curve of NC (right) in 100MDA;

[0048] Figure 31 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SAStandard curves of peak NC anode current versus square root of different scan rates;

[0049] Figure 32 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC (left) and Comparative Example 1 SA Standard curve of CV peak redox potential versus scan rate logarithm for NC (right);

[0050] Figure 33 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Cyclic stability test of NC in saturated DA solution;

[0051] Figure 34 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The dissolution of iron in the electrolyte after NC oxidation with DA for 1 hour;

[0052] Figure 35 I prepared in Example 1 of the present invention 0.3 / Fe SA A diagram illustrating the reasons for the improved NC stability;

[0053] Figure 36 I prepared in Example 1 of this invention 0.3 / Fe SA The DPV response of NC-modified electrode to different concentrations of DA;

[0054] Figure 37 Fe prepared for Comparative Example 1 SA The DPV response of the NC-modified electrode to different concentrations of DA (a) and the corresponding calibration curves (b);

[0055] Figure 38 For the selectivity of DA detection;

[0056] Figure 39 I prepared according to Example 1 0.3 / Fe SA Performance changes of NC-fabricated sensors after 20 days of storage;

[0057] Figure 40 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA DPV response of NC-modified electrode in the presence of 100 μMDA, UA and AA;

[0058] Figure 41 I prepared in Example 1 of the present invention 0.3 / Fe SA DPV response of NC-modified electrode to different concentrations of UA (a) and I 0.3 / FeSANC's UA detection calibration curve (b);

[0059] Figure 42 Fe prepared as Comparative Example 1 of this invention SA DPV response of NC-modified electrode to different concentrations of UA (a) and Fe-based SA NC's UA detection calibration curve (b);

[0060] Figure 43 I prepared in Example 1 of the present invention 0.3 / Fe SA DPV response of NC-modified electrode to different concentrations of AA (a) and I 0.3 / FeSANC's AA detection calibration curve (b);

[0061] Figure 44 Fe prepared as Comparative Example 1 of this invention SA DPV response of NC-modified electrode to different concentrations of AA (a) and Fe-based SA NC's AA test calibration curve (b);

[0062] Figure 45 A heatmap of the data matrix for DA and UA from the electrochemical sensor;

[0063] Figure 46 This is a two-dimensional standard fraction graph of the electrochemical sensor under the action of DA and UA. Detailed Implementation

[0064] 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.

[0065] 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. Every smaller range between any stated value or intermediate value within a stated range, and 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.

[0066] 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 or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0067] 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 obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0068] 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.

[0069] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0070] All raw materials used in the following embodiments of the present invention are commercially available. The silica used in the present invention is liquid silica, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.

[0071] The following embodiments are further illustrations of the technical solution of the present invention.

[0072] Example 1

[0073] Weigh out 334 mg ZnCl2, 150 mg FeCl2, 2.5 g glucosamine hydrochloride, 2.5 g dicyandiamide, 5 mL SiO2, and 0.3 g KI, dissolve them in 25 mL deionized water, mix and stir for 2 hours, and freeze-dry to obtain a yellow powder. Anneal the obtained powder in N2 at 900 °C for 2 hours at a heating rate of 5 °C / min. Etch the obtained black powder with hydrofluoric acid (10% mass concentration) for 24 hours, centrifuge, wash three times with water and ethanol, and dry at 60 °C. The resulting catalyst is denoted as I. 0.3 / Fe SA NC.

[0074] Example 2

[0075] Same as Example 1, except that the amount of KI added is 0.1g, and the resulting catalyst is denoted as I. 0.1 / Fe SA NC.

[0076] Example 3

[0077] Same as Example 1, except that the amount of KI added was 0.4g, and the resulting catalyst was denoted as I. 0.4 / Fe SA NC.

[0078] Comparative Example 1

[0079] Same as Example 1, except that the amount of KI added was 0g, and the resulting catalyst was denoted as Fe. SA NC.

[0080] Preparation of the working electrode:

[0081] First, the glassy carbon electrode (GCE) was polished sequentially with 0.3 μm and 0.05 μm alumina polishing powders. Then, the electrode was ultrasonically cleaned with distilled water and ethanol, respectively, and air-dried at room temperature or dried with an infrared lamp. Next, the I / Fe... SA NC and Fe SA NC was dispersed in a mixture of deionized water, anhydrous ethanol, and 5% Nafion (volume ratio 50:49:1) to prepare an ink concentration of 1 mg / mL. Then, 5 μL of the ink was dropped onto the electrode and allowed to dry into a film before testing.

[0082] 1.I / Fe SA Synthesis and characterization of NC

[0083] 1. Figure 1 Preparation of I / Fe for embodiments of the present invention SA A schematic diagram of the synthesis of NC. It can be seen that the catalyst I / Fe prepared in this invention... SA NC is synthesized using silicon dioxide as a template. Specifically, it involves using dicyandiamide as the nitrogen source and potassium iodide as the iodine source, pyrolyzing at 900°C for 2 hours, and then etching with hydrofluoric acid to obtain atomically dispersed I / Fe. SA NC.

[0084] 2. Figure 2 From top to bottom, the images show the I / Fe prepared in Example 1, Comparative Example 1, Example 2, and Example 3 of this invention. SA Transmission electron microscopy (TEM) images of NC, with the inset of the first image showing I prepared in Example 1. 0.3 / Fe SA SAED pattern of NC. I / Fe can be observed from the transmission electron microscope image. SA NC and Fe SA The NC clearly shows a porous nanostructure (approximately 20 nm), and selected area electron diffraction (inset) results indicate that I 0.3 / Fe SA NC has low crystallinity and exhibits an amorphous graphite structure.

[0085] 3. Figure 3 I prepared in Example 1 of the present invention 0.3 / Fe SA The HRTEM image of NC also shows some smaller mesopores (approximately 10-20 nm).

[0086] 4. Figure 4 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA AC-HAADF-STEM images of NC. Aberration-corrected high-angle annular dark-field scanning TEM (AC-HAADF-STEM) images validate I. 0.3 / Fe SA NC and Fe SA In NC, the atomic dispersion of individual iron atoms is shown. Bright spots of different intensities with uniform distribution are marked with blue and yellow circles, respectively, and identified as Fe atoms and I atoms by Z-comparison analysis (the inset in Figure b is a topographic map obtained by software processing, and the height represents the intensity of the atoms in Figure b; the inset in Figure c is the intensity of the atoms in the direction indicated by the arrow in the rectangle).

[0087] 5. Figure 5 I prepared in Example 1 of the present invention 0.3 / Fe SA The elemental spectrum image of NC. It can be seen that C, N, I and Fe elements can be detected based on the energy-dispersive X-ray spectroscopy (EDS) spectrum.

[0088] The I / Fe ratios prepared in Examples 1, 2, and 3 were determined by inductively coupled plasma mass spectrometry (ICP-MS). SA Fe prepared by NC and Comparative Example 1 SA NC, discovered I 0.3 / Fe SA NC and Fe SA The iron content in NC is 2.08 and 2.7 wt% respectively (Table 1), which is consistent with the low metal content characteristic of single-atom materials.

[0089] Table 1. ICP-MS results of different samples

[0090]

[0091] 6. Figure 6 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SAX-ray diffraction (XRD) pattern of NC. The image shows two broad peaks observed near 25° and 43°, which can be attributed to the 002 and 101 planes of graphitic carbon. No characteristic crystalline peaks of iron were detected, indicating the absence of iron nanoparticles.

[0092] 7. Figure 7 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SA The Raman spectrum of NC. As can be seen from the figure, at 1350 cm⁻¹... -1 and 1580cm -1 Two distinct peaks were observed, corresponding to the D and G bands of graphene, respectively. With increasing I doping concentration, the ID / IG ratio increased from 1.203 to 1.263; a high ID / IG ratio indicates a high degree of defect.

[0093] 8. Figure 8 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA NC adsorption-desorption isotherms and pore size distribution in N2. From Figure 8 As can be seen from 'a' in the graph (the black line is the adsorption curve, and the red line is the desorption curve), Fe... SA NC and I 0.3 / Fe SA The specific surface areas of NC are 481.2 and 328.1 m², respectively. 2 / g, the addition of iodine resulted in a slight decrease in specific surface area. (See figure) Figure 8 As shown in b, the pore sizes of the prepared single-atom catalyst are mainly around 4 nm and 20 nm. The mesopores at 20 nm are generated by the etching of SiO2, while the micropores at 4 nm are generated by the volatilization of ZnCl2. Fe SA NC and I 0.3 / Fe SA The total pore volume of NC is 1.300 cm³. 2 / g and 1.060cm 2 / g, the reduction in total pore volume may be related to the introduction of iodine.

[0094] 9. Figure 9 The diagrams show the structure and catalytic mechanism of the I / FeSANC and natural heme prepared in this invention. It can be seen that mimicking the composition and geometry of the active site of the natural enzyme can improve the catalytic performance, while iodine doping induces a series of electron transfer processes.

[0095] 10. Figure 10 I prepared in Example 1 of the present invention 0.3 / Fe SAFe prepared by NC and Comparative Example 1 SA X-ray photoelectron spectroscopy (XPS) spectrum of NC. This figure shows I 0.3 / Fe SA NC and Fe SA NC has similar C, N, O, and Fe peaks, while I 0.3 / Fe SA NC showed an additional I3d peak at 0.22 at%.

[0096] 11. Figure 11 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA High-resolution XPS I 3d spectrum of NC. The figure shows the I / Fe ratio. SA NC contains two types of iodine, including ionic iodine (Cl). + -C(3d 5 / 2 618.90eV and 3d 3 / 2 630.36 eV) and covalently bound iodine CI (3d 5 / 2 620.50eV and 3d 3 / 2 (631.99 eV). No I2-related signal peak was observed at 619.9 eV, indicating that iodine is incorporated into the carbon structure through chemical bonds with carbon atoms, and does not exist in the form of iodine molecules.

[0097] 12. Figure 12 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA High-resolution XPS Fe 2p spectrum from NC. The figure shows that the peaks at 709.39 and 722.4 eV belong to Fe. 2+ 2p 3 / 2 and 2p 1 / 2 The peaks at 711.7 and 725.6 eV belong to Fe orbitals. 3+ 2p 3 / 2 and 2p 1 / 2 Orbital. The Fe(0) peaks are absent at 719.7 and 707.4 eV, indicating that only oxidized Fe exists, primarily in the +2 valence state. I 0.3 / Fe SA The binding energy of NC is greater than that of Fe. SA The NC value is about 0.14 eV higher, indicating that the oxidation state of iron increases slightly after the addition of iodine.

[0098] 13. Figure 13 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1SA High-resolution XPS C 1s spectrum of NC. The figure shows that a CI bond is formed at 285.8 eV.

[0099] 14. Figure 14 The I / Fe prepared in Examples 1, 2, and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SA The high-resolution XPS N 1s spectrum of NC. It can be seen that the N 1s spectrum is decomposed into five N substances: pyridine N (398.2 eV), MN (399.4 eV), pyrrole N (400.8 eV), graphite N (401.6 eV), and N-oxide (403.4 eV).

[0100] 15. Figure 15 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA The figure shows the Fe-K-edge XANES spectra compared to those of NC, Fe foil, FeO, Fe2O3, and FePc (the inset shows the determination of the oxidation state of Fe using the first derivative curve of the Fe K-edge XANES spectrum; the oxidation state is linearly correlated with the absorption position of the K-edge). It can be seen from the figure that I / Fe... SA NC and Fe SA The absorption edge energies of NC are all between those of Fe foil and FeO, confirming that the oxidation state of Fe is between 0 and +2. Iodine doping slightly increases the valence state of Fe, which is consistent with the XPS results. Figure 16 ).

[0101] 16. Figure 16 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA The first derivative curves of the Fe-K edge XANES compared to NC, Fe foil, FeO and Fe2O3.

[0102] 17. Figure 17 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA EXAFS fitting curves for NC, Fe foil, and FePc in R space. It can be seen that the 1s→4pz electronic transition of FePc produces a characteristic peak near 7116 eV, which can be attributed to the FeN4 moiety. This is evident in the I... 0.3 / Fe SA NC and Fe SA They can also be observed in NC, indicating that they retain D4h symmetry around Fe.

[0103] 18. Figure 18 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference sample (Fe) SA NC) EXAFS Fourier Transform (EXAFS-FT) curve. I 0.3 / Fe SA NC and Fe SA The EXAFS Fourier transform (EXAFS-FT) of NC showed a main peak at 1.46 Å, corresponding to the Fe-N / O scattering path, while no Fe-Fe binding was observed at 2.2 Å, indicating that Fe atoms were dispersed in both samples.

[0104] 19. Figure 19 I prepared in Example 1 of the present invention 0.3 / Fe SA NC and reference samples (Fe foil, FePc and Fe) SA The FeK edge EXAFS-WT plot of NC). Wavelet transform (WT) EXAFS characterizes the prepared Fe. SA NC and I 0.3 / Fe SA The atomic configuration of NC differs from the WT signal of Fe foil and FePc. SA NC and I 0.3 / Fe SA No iron-iron bonds were observed in NC, which further confirms the presence of atomically dispersed iron atoms.

[0105] It is noteworthy that the possibility of Fe-I bond formation can be ruled out since no relevant peaks were observed in the EXAFS-FT and EXAFS-WT spectra. Quantitative structural results were extracted using least-squares EXAFS curve fitting analysis (Table 2), indicating that the I / Fe... SA NC and Fe SA The iron coordination numbers in NC are similar, close to 5.0, with FeSANC at 4.9, and the I / Fe ratio is... SA NC is 5.3.

[0106] Table 2. Results of ICP-MSEX AFS curve fitting analysis for different samples (S0) 2 =0.702)

[0107]

[0108]

[0109] Note: CN a -Coordination number; R b -bond length; σ 2c- The Debye-Waller factor explains thermal and structural disorder; ΔE0 d - Internal potential correction; R coefficient represents the goodness of fit. By fixing CN to a known crystallinity value, and fitting the experimental EXAFS of the Fe foil, S0 2 It was fixed at 0.702. Fit range: and (Fe foil); and (Fe SA NC, I / Fe SA (NC, FePc, FeO, and Fe2O3). Reasonable range for EXAFS fitting parameters: 0.700 <S0 2 <1.000; CN>0; ΔE0 < 10 eV; R < 0.02.

[0110] 20. To better understand the banded structure and reveal the I / Fe ratio SA To investigate the mechanism of NC performance improvement, this invention employs ultraviolet photoelectron spectroscopy (UPS) analysis. Figure 20 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The magnified UPS spectrum of NC. As can be seen from the figure, Fe... SA NC and I 0.3 / Fe SA The cutoff energy of NC (E) cutoff The values ​​are 16.47 and 16.86 eV, respectively. According to e... Φ =21.22eV-E cutoff Equations, calculate their work functions (e Φ The values ​​were 4.75 and 4.36 eV, respectively, indicating that I 0.3 / Fe SA NC tends to donate more electrons to the OH intermediate. Furthermore, Fe... SA NC and I 0.3 / Fe SA The highest occupied molecular orbital (HOMO) energies of NC are 1.27 and 1.46 eV, respectively, indicating that the introduction of I leads to the delocalization of iron 3d electrons and a thinning of the electron density at the iron center. Generally, charge redistribution is accompanied by a change in the 3d electron spin configuration.

[0111] 21. The present invention performs temperature-varying inductance (MT) measurements to describe changes in electron spin state. Figure 21 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SANC's χ m And 1 / χ² plot. The plot shows Fe SA NC and I / Fe SA NC exhibits paramagnetism that is almost temperature-independent. From 1 / χ m The figure shows that the introduction of I weakens the paramagnetic state of the FeN5 molecule. This indicates a reduction in the number of free electrons with Pauli paramagnetism moving around the Fe(II) center, which is in good agreement with the XPS results. Furthermore, this invention also yielded an effective magnetic moment (μ). eff It is related to the number of unpaired d electrons (n) of the Fe(II) ion, and the calculation formula is as follows ( Figure 21 (Illustrations in the text)

[0112] The increase in μeff indicates that I 0.3 / Fe SA The number of unpaired d electrons in NC iron(II) ions is much greater than that in the original Fe. SA NC. This indicates that I 0.3 / Fe SA NC undergoes a spin transition, allowing more single-occupied 3d electrons to easily transfer to the dz2 orbital of O, thus exhibiting higher catalytic activity.

[0113] II. Electrochemical DA Oxidation Performance and Stability Testing

[0114] 1. Figure 22 This is a schematic diagram of DA oxidation.

[0115] 2. Use [Fe(CN)6] 3- / 4- As a redox probe, cyclic voltammetry (CV) tests were performed on a series of control materials. Figure 23 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Cyclic voltammetry curves of NC. Obvious reversible redox peaks were observed in all CV results, with I... 0.3 / Fe SA The redox peak of NC is higher than that of Fe. SA NC and bare glass carbon electrode (GCE). Calculations show that GCE, Fe... SA NC / GCE and I / Fe SA The electrochemical active areas of NC / GCE were 0.116 cm², 0.123 cm², and 0.129 cm², respectively. This indicates that iodine doping significantly improves its inherent conductivity, making the electrode more compatible with K₃[Fe(CN)₆]. 3- / 4- More active electron transfer between probes is beneficial for improving the interface redox process.

[0116] Calculation of electrochemical active area:

[0117] The electrochemical active area of ​​the modified electrode can be calculated using the Randles-Sevcik equation. The equation is as follows:

[0118] Ip = 2.69 × 10 5 AD 1 / 2 n 3 / 2 γ 1 / 2 C

[0119] Where A is the area of ​​the electroactive surface region (cm²) 2 D is the diffusion coefficient of the molecule in the solution (6.70 ± 0.02 × 10⁻⁶ cm⁻¹). 2 / s), where n is the number of electrons participating in the redox reaction (for [Fe(CN)6)] 3- / 4- For example, n = 1), γ is the scan rate of the potential perturbation (V / s), and C is the concentration of the redox probe (mol / cm³). -3 ).

[0120] 3. Figure 24 [Fe(CN)6] 3- / 4- I prepared in solution in Example 1 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The electrochemical impedance spectroscopy (EIS) of NC shows that I 0.3 / Fe SA The electron transfer resistance of NC / GCE is lower than that of bare GCE and Fe. SA NC / GCE, which is consistent with the CV results above.

[0121] 4. Figure 25 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The linear sweep frequency voltammetry (LSV) curve of NC shows that the modified electrode has a large potential window (~3V), indicating that no other reaction interferes with DA oxidation.

[0122] 5. This invention further investigated the application of DA in Fe using both CV and differential pulse voltammetry (DPV). SA NC / GCE and I 0.3 / Fe SA Oxidation on the NC / GCE electrode. Figure 26 Fe with or without DA in PBS (0.1M pH=7.4) SA NC and I 0.3 / Fe SA The CV curve of NC. It can be seen that I...0.3 / Fe SA The peak DA oxidation current of NC / GCE is higher than that of Fe. SA NC / GCE, this indicates that I 0.3 / Fe SA NC compared to Fe SA NC exhibits higher catalytic activity.

[0123] 6. Figure 27 Fe with or without DA in PBS (0.1M pH=7.4) SA NC and I 0.3 / Fe SA The DPV response of NC. It can be seen that I 0.3 / Fe SA NC is not only more than Fe SA NC showed higher current and lower oxidation potential, which further confirms that I doping can significantly improve catalytic activity.

[0124] 7. Figure 28 The I / Fe prepared in Examples 1, 3 and 3 of this invention SA Fe prepared by NC and Comparative Example 1 SA Sensitivity of NC to oxidation by 100M DA. As can be seen from the figure, compared with Fe... SA Compared to NC, I / Fe with different iodine doping levels SA NC shows higher sensitivity to DA oxidation, which demonstrates the feasibility of the iodine doping strategy in improving detector sensitivity.

[0125] 8. Figure 29 I prepared in Example 1 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The ampere reaction of NC with DA. As shown in the graph, taking 100M DA as an example, Fe... SA NC and I 0.3 / Fe SA The response times of NC were 16.41 seconds and 6.93 seconds, respectively, indicating that I 0.3 / Fe SA NC's response speed is faster than Fe SA NC is fast. The electron transport kinetics of DA oxidation were tested by adjusting the CV scan rate.

[0126] 9. Figure 30 I prepared in Example 1 at different scan rates (10-250 mV / s) 0.3 / Fe SA Fe prepared by NC (left) and Comparative Example 1 SACV curve of NC (right) in 100MDA. As can be seen from the figure, with the increase of scan rate, the oxidation peak current and reduction peak current of all modified electrodes increase significantly.

[0127] 10. Figure 31 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The standard curves of the peak NC anode current versus the square root of different scan rates show that the oxidation peak current has a linear relationship with the square root of the scan rate, verifying that DA oxidation is a diffusion-controlled process.

[0128] 11. Figure 32 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC (left) and Comparative Example 1 SA The standard curve of the CV peak redox potential versus the logarithm of the scan rate for NC (right). The figure shows that the peak spacing between the anodic and cathode peaks increases with increasing scan rate, indicating quasi-reversible behavior. It can be seen that I... 0.3 / Fe SA The slope of NC is higher than that of Fe. SA NC indicates a larger charge transfer coefficient α and faster electron transfer. The calculated I... 0.3 / Fe SA NC and Fe SA The electron transfer rate constant Ks for NC is 1.487 s⁻¹. -1 and 1.019s -1 , showing that DA and I 0.3 / Fe SA The electron transfer dynamics between NCs are indeed faster.

[0129] Methods for calculating the electron transfer rate constant (Ks) in a reaction process:

[0130] The oxidation-reduction peak separation potential increases with increasing scan rate, indicating that charge transfer kinetics limit DA oxidation. Using the relationship between peak potential and scan rate, the Ks between DA and the modified electrode is evaluated using the Lavignon equation, as shown below:

[0131] E PA =E 0 +[2.3RT / (1-ɑ)nF]logν

[0132] E PC =E 0 -(2.3RT / ɑnF)logν

[0133] log K S =ɑlog(1-ɑ)-(1-ɑ)logɑ-log(RT / nFν)-(1-ɑ)ɑnFΔEp / 2.3RT

[0134] Where: K S is the electron transfer rate constant; 2.3RT / (1-ɑ)nF and -2.3RT / ɑnF correspond to the slopes of oxidation and reduction, respectively; ΔE is the peak separation of the DA redox couple. Calculated according to the above formula, I... 0.3 / Fe SA NC and Fe SA The electron transfer rate constant Ks for NC is 1.487 s⁻¹. -1 and 1.019s -1 .

[0135] 12. Figure 33 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA Cyclic stability test of NC in saturated DA solution. As shown in the figure, after 30 oxidation cycles in saturated DA solution, I... 0.3 / Fe SA The oxidation peak current of NC is 33.7% of the initial peak current, while Fe SA The oxidation peak current of NC is only 16.4% of the initial peak current. It is speculated that the current decay may be caused by structural instability, and oxidation is accompanied by the dissolution of active sites.

[0136] 13. Figure 34 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The dissolution of iron in the electrolyte after 1 hour of DA oxidation was investigated. Electrochemical iron dissolution was monitored by ICP-MS. After 1 hour of DA oxidation, I... 0.3 / Fe SA The free iron content in NC electrolyte is lower than that in Fe. SA NC electrolyte, which indicates that I 0.3 / Fe SA The structure of NC is more than that of Fe SA NC is more stable. These results are consistent with the results of the cycle stability test.

[0137] 14. Figure 35 I prepared in Example 1 of the present invention 0.3 / Fe SA A diagram illustrating the reasons for the improved NC stability. As can be seen from the diagram, I... 0.3 / Fe SAThe enhanced stability of NC is due to the electronic effects induced by I doping weakening the protonation process of N and reducing H. + The attack on the active center inhibits the dissolution of Fe sites.

[0138] III. Electrochemical DA Detection

[0139] 1. Considering I 0.3 / Fe SA The excellent sensitivity of NC in the DA oxidation reaction will be further investigated in the future. 0.3 / Fe SA The performance of NC in detecting DA. Figure 36 I prepared in Example 1 of this invention 0.3 / Fe SA The DPV reaction of the NC-modified electrode with different concentrations of DA is shown in the figure. As can be seen from the figure, the oxidation peak current at 0.2 V gradually increases with the increase of DA concentration.

[0140] 2. Figure 37 Fe prepared for Comparative Example 1 SA The DPV response of the NC-modified electrode to different concentrations of DA (a) and the corresponding calibration curves (b). Based on the established relationship between peak current and DA concentration, the detection limit (LOD) was calculated to be 4.186 nM, which is lower than that of Fe. SA The NC-modified electrode has a molecular weight of 31.74 nM.

[0141] 3. Specificity is an important parameter for excellent sensors, especially in the presence of various organic and inorganic interfering substances. Figure 38 The figure shows the selectivity of DA detection. As can be seen from the figure, no significant current response was observed after the successive addition of potential interfering substances such as 2 mM NaCl, KCl, MgCl2, Glu, and Cys. Furthermore, a distinct oxidation peak appeared upon the addition of 100 μM DA, indicating that the proposed electrochemical sensor exhibits good selectivity.

[0142] 4. Figure 39 I prepared according to Example 1 0.3 / Fe SA The performance changes of the NC-fabricated sensor after 20 days of storage. As can be seen from the figure, the sensor maintains good detection performance after 20 days of storage, demonstrating good stability.

[0143] 5. To further investigate the practical feasibility of this sensor in serum samples, the standard addition method was employed. DA was not detected in the initial serum sample, and the detected DA concentration after addition was essentially consistent with the actual added DA concentration. As shown in Table 3, the recovery rate ranged from 99.35% to 108.38%, indicating that the electrochemical sensor has good feasibility in actual sample analysis.

[0144] Table 3

[0145]

[0146] 6. The redox potentials of DA, uric acid (UA), and ascorbic acid (AA) are close and often overlap, so it is necessary to distinguish between DA and UA and AA. Figure 40 I prepared in Example 1 of the present invention 0.3 / Fe SA Fe prepared by NC and Comparative Example 1 SA The DPV response of the NC-modified electrode in the presence of 100 μM DA, UA, and AA. As shown in the figure, the oxidation peaks of UA and AA appear near 0.33 V and -0.04 V, respectively. 0.3 / Fe SA NC showed higher DPV responses to both substances than Fe. SA NC indicates I 0.3 / Fe SA NC has a stronger catalytic effect on UA ​​and AA.

[0147] 7. Figure 41 I prepared in Example 1 of the present invention 0.3 / Fe SA DPV response of NC-modified electrode to different concentrations of UA (a) and I 0.3 / Fe SA NC's UA test calibration curve (b). Figure 42 Fe prepared as Comparative Example 1 of this invention SA DPV response of NC-modified electrode to different concentrations of UA (a) and Fe-based SA NC's UA test calibration curve (b). Figure 43 I prepared in Example 1 of the present invention 0.3 / Fe SA The DPV response (a) of the NC-modified electrode to different concentrations of AA and based on I0.3 / Fe SA NC's AA test calibration curve (b). Figure 44 Fe prepared as Comparative Example 1 of this invention SA DPV response of NC-modified electrode to different concentrations of AA (a) and Fe-based SA NC's AA test calibration curve (b). By comparison... Figures 41-44 It can be observed that, with Fe SA Compared to NC, I 0.3 / Fe SA NC has a lower LOD.

[0148] Table 4 shows the detection range and LOD of DA, UA, and AA sensors.

[0149]

[0150]

[0151] 8. To evaluate the resolution performance of the proposed electrochemical sensor, this invention successfully used Fe based on machine learning algorithms. SA NC and I 0.3 / Fe SA NC distinguished three equal concentrations of DA, UA, and AA. Correspondingly, heatmaps, or "fingerprints," of the responses to DA, UA, and AA were generated, revealing the feasibility of this electrochemical sensor array in distinguishing DA, UA, and AA. Figure 45 Then, linear discriminant analysis (LDA) was performed using the two most important discriminant factors, and the resulting data matrix was transformed into a visualized two-dimensional standard score plot. Figure 46 The linear discriminant analysis results show that DA, UA, and AA can be completely separated without errors or misclassifications (Table 5).

[0152] Table 5 Training matrices for DA, UA, and AA recognition

[0153]

[0154] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing an iodine atom-doped catalyst, characterized in that, The iodine atom-doped catalyst has an active center FeN5. Iodine is chemically bonded to the carbon structure through bonds with carbon atoms. The process includes the following steps: using zinc chloride, ferrous chloride, glucosamine hydrochloride, dicyandiamide, liquid silica, and potassium iodide as raw materials, and deionized water as a solvent, the raw materials are dissolved in the solvent, mixed and stirred, and freeze-dried to obtain a yellow powder. The obtained yellow powder is then annealed under a nitrogen atmosphere. The resulting black powder is etched with hydrofluoric acid, and after centrifugation, washing, and drying, the iodine atom-doped catalyst is obtained. The ratio of zinc chloride, ferrous chloride, glucosamine hydrochloride, dicyandiamide, liquid silica, and potassium iodide is 0.334 g : 0.15 g : 2.5 g : 2.5 g : 5 mL : (0.1-0.4) g; The annealing parameters are: heating rate 5℃ / min, temperature 900℃, and holding time 2h. The hydrofluoric acid has a mass concentration of 10%; the etching time is 24 hours.

2. The application of an iodine atom-doped catalyst prepared by the method described in claim 1 in the preparation of electrode materials, characterized in that, The iodine atom-doped catalyst was dispersed in a solvent to obtain an ink with a concentration of 1 mg / mL. The ink was then dropped onto a glassy carbon electrode material and dried to form a film.

3. The application according to claim 2, characterized in that, The solvent in which the iodine atom-doped catalyst is dispersed is a mixture of water, ethanol, and a 5% (w / w) perfluorosulfonic acid polymer solution, in a volume ratio of 50:49:

1.

4. The application of an iodine atom-doped catalyst prepared by the preparation method of claim 1 in a sensor.

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