MXene / Mn2O3 / PtSA composite material and preparation method thereof, electrochemical sensor and electrochemical detection method of dopamine and / or uric acid

Abstract

The invention relates to an MXene / Mn2O3 / PtSA composite material and a preparation method thereof, an electrochemical sensor and an electrochemical detection method of dopamine and / or uric acid. According to the method, high-conductivity MXene is used as a substrate material, Mn2O3 is used as a carrier, a Pt single atom is used as an active center, and the Pt single atom is limited in the Mn2O3 carrier. The invention discloses a preparation method of the Pt monatomic composite material, and the preparation method adopts a simple three-step method, namely three steps of stirring and mixing, freeze-drying and calcining. According to the prepared catalyst, aggregation of Pt single atoms is effectively avoided, charge distribution of the Pt single atoms is adjusted, and therefore the catalytic performance of a Pt single atom composite material is improved. The prepared Pt monatomic composite material is dispersed into printing ink, then the printing ink is dispensed on the surface of an electrode and dried, and the obtained sensing electrode can be used for independent and simultaneous detection of dopamine and uric acid.

Description

Technical Field

[0001] This application relates to the fields of analytical chemistry and nanomaterials, and in particular to an MXene / Mn2O3 / Pt SA Composite materials and their preparation methods, electrochemical sensors, and electrochemical detection methods for dopamine and / or uric acid. Background Technology

[0002] Uric acid and dopamine, as important bioactive small molecules, have attracted much attention in personalized testing. Uric acid is the final metabolic product of the liver's breakdown of purine compounds, and its level is maintained by a dynamic balance between production and excretion. Disruption of this balance can lead to various diseases, such as hyperuricemia, gout, and cardiovascular diseases. On the other hand, dopamine, as the most abundant catecholamine neurotransmitter in the brain, directly participates in the regulation of the central nervous system, and its abnormal concentration is closely related to various neurological diseases such as Parkinson's disease, schizophrenia, and Tourette syndrome. Previous studies have shown that uric acid has a certain protective effect on dopamine neurons in Parkinson's disease patients, and that uric acid levels affect the development of Parkinson's disease. Therefore, simultaneous detection of uric acid and dopamine not only has important clinical value but also helps to reveal the potential link between the two. However, due to their high similarity in chemical structure and redox potential, efficient and accurate simultaneous detection still faces significant challenges.

[0003] Over the past few decades, various methods for detecting uric acid and dopamine have been developed, including high-performance liquid chromatography-mass spectrometry, fluorescence analysis, and spectrophotometry. While these methods achieve detection, they are typically cumbersome, costly, time-consuming, and rely on complex specialized instruments, limiting their widespread adoption in rapid diagnostics and clinical applications. In contrast, electrochemical detection techniques offer unique advantages due to their ease of operation, rapid response, high sensitivity, low cost, and good selectivity. However, the accuracy and sensitivity of electrochemical detection largely depend on the performance of the electrode materials. In recent years, the emergence of single-atom catalytic materials has provided a new opportunity to address this issue. By dispersing active centers at the atomic level, single-atom materials not only maximize atomic utilization but also, due to their well-defined electronic coordination structure, facilitate precise control of the electrochemical reaction process. This structural characteristic endows single-atom materials with superior catalytic activity and selectivity, providing a new approach to solving the challenge of simultaneously detecting dopamine and uric acid. Summary of the Invention

[0004] Based on the above problems, the purpose of this invention is to provide an MXene / Mn2O3 / Pt SAA composite material comprising a substrate, a carrier, and an active center; the substrate is a conductive material; the carrier is a metal oxide loaded on the substrate; and the active center is an atomically dispersed Pt single atom, wherein the Pt single atom is confined within the metal oxide.

[0005] Furthermore, the conductive material is selected from one or more of graphene, carbon nanotubes, MXene, carbon fibers, hollow carbon spheres, and reduced graphene oxide.

[0006] Furthermore, the metal oxide precursor is selected from metal nitrates, including one or more of Co(NO3)2∙6H2O, Zn(NO3)2∙6H2O, Ni(NO3)2∙6H2O, Fe(NO3)3∙9H2O, Mn(NO3)2∙4H2O or In(NO3)3∙xH2O.

[0007] A further MXene / Mn2O3 / Pt SA The method for preparing composite materials includes the following steps: S1. Disperse the conductive material in deionized water and stir to obtain dispersion A; S2. The metal oxide precursor and the Pt precursor are dispersed together in deionized water and ultrasonically treated to obtain dispersion B; wherein the molar ratio of the metal element in the metal oxide precursor to the platinum element in the Pt precursor is (50-1000):1. S3. Mix the dispersion B with the dispersion A and stir to obtain a mixture; S4. The mixture is freeze-dried to obtain a solid precursor; S5. The solid precursor is calcined in an oxygen-containing atmosphere to obtain the MXene / Mn2O3 / Pt. SA Composite materials.

[0008] Furthermore, in step S2, the metal oxide precursor is a metal nitrate, and the Pt precursor is PtCl4; the molar ratio of the metal element to the platinum element is 100:1. Furthermore, the metal nitrate is manganese nitrate tetrahydrate (Mn(NO3)2∙4H2O).

[0009] Furthermore, in step S1, the dispersion concentration of the conductive material in deionized water is from 5 mg / mL to 50 mg / mL.

[0010] Furthermore, in step S5, the calcination temperature is 200-350℃, the calcination time is 1-24 hours, and the heating rate is 1-15℃ / min.

[0011] Furthermore, the calcination temperature is 250℃ and the calcination time is 5 hours.

[0012] Furthermore, in step S2, the Pt precursor is selected from one or more of chloroplatinic acid, platinum dichloride, platinum tetrachloride, sodium chloroplatinate, sodium chloroplatinate, potassium chloroplatinate, or potassium chloroplatinate.

[0013] Furthermore, in step S4, the freeze-drying time is 10 to 48 hours.

[0014] Furthermore, an electrochemical sensor includes a Pt single-atom composite material modified working electrode, wherein the Pt single-atom composite material modified working electrode employs the MXene / Mn2O3 / Pt as described in any one of claims 1-3. SA Composite material or MXene / Mn2O3 / Pt prepared by the preparation method according to any one of claims 4-11 SA The modification method of the Pt single-atom composite material includes: mixing the Pt single-atom composite material with deionized water, ethanol and Nafion solution in a certain proportion to prepare a modification ink, applying the modification ink to the electrode surface, and drying it to obtain the final product.

[0015] Furthermore, in the modified ink, the volume fraction of Nafion is 1% to 10%, the volume fraction of deionized water is 30% to 80%, and the volume fraction of ethanol is 40% to 70%.

[0016] Furthermore, the concentration of Pt single-atom composite material in the modified ink is from 0.1 mg / mL to 5 mg / mL.

[0017] Furthermore, the amount of the modifying ink drop-coated onto the electrode is 5 μL to 10 μL.

[0018] Furthermore, an electrochemical detection method for dopamine and / or uric acid, using the aforementioned electrochemical sensor, includes the following steps: immersing the working electrode of the electrochemical sensor in a phosphate buffer solution containing the analyte, employing a three-electrode system, and using differential pulse voltammetry for detection to obtain a differential pulse voltammogram; wherein the pH value of the phosphate buffer solution is 3 to 12.

[0019] Furthermore, the analyte is dopamine, uric acid, or a mixture of both.

[0020] By employing the above technical solution, the effective gains of the present invention are: (1) The Pt single-atom composite material preparation method used in this invention is simple and can be prepared in air atmosphere and at low calcination temperature, which is expected to achieve large-scale preparation; (2) In this invention, MXene serves as a highly conductive substrate, ensuring efficient electron transport in the final composite material. The metal oxide Mn2O3 and Pt single atoms react synchronously, allowing the Pt single atoms to be stably anchored on Mn2O3, effectively preventing the aggregation of Pt single atoms and maximizing their utilization. This anchoring also facilitates further electron transfer from the Pt single atoms to Mn2O3, improving catalytic performance. The Pt single-atom composite material obtained in this invention can be used for the individual and simultaneous detection of dopamine and uric acid. Attached Figure Description

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings: Figure 1 The image shown is a scanning electron microscope image of the Pt single-atom composite material provided in an embodiment of the present invention; Figure 2 The image shown is a transmission electron microscope (TEM) image of the Pt single-atom composite material provided in an embodiment of the present invention; wherein... Figure 2 a is MXene / Mn2O3 / Pt SA Low-magnification transmission electron microscope image; Figure 2 b is MXene / Mn2O3 / Pt SA High-magnification transmission electron microscope images; Figure 3 This shows a high-angle annular dark-field scanning transmission electron microscope image of the Pt single-atom composite material provided in an embodiment of the present invention; Figure 4 The X-ray photoelectron spectrum of Pt element in the Pt single-atom composite material provided in this embodiment of the invention is shown; wherein Figure 4 a is the Pt 4f XPS fitted spectrum of Pt / C; Figure 4 b is MXene / Mn2O3 / Pt SA The Pt 4f XPS fitting spectrum; Figure 5 The differential pulse voltammograms and corresponding linear relationships of the electrochemical sensor based on Pt single-atom composite materials provided in this embodiment of the invention for detecting different concentrations of DA individually are shown; wherein... Figure 5 a is MXene / Mn2O3 / Pt SA Differential pulse voltammetric response of the electrode to different concentrations of DA; Figure 5 b is Figure 5 The corresponding calibration curve for a; Figure 5 c is Figure 5 The calibration curve for the first linear interval in b.

[0022] Figure 6The differential pulse voltammograms and corresponding linear relationships of the electrochemical sensor based on Pt single-atom composite materials provided in this embodiment of the invention for detecting different concentrations of UA individually are shown; wherein Figure 6 a is MXene / Mn2O3 / Pt SA Differential pulse voltammetric response of the electrode to different concentrations of UA; Figure 6 b is Figure 6 The corresponding calibration curve for a; Figure 6 c is Figure 6 The calibration curve for the first linear interval in b; Figure 7 The differential pulse voltammograms and corresponding linear relationships of the electrochemical sensor based on Pt single-atom composite materials provided in this embodiment of the invention for mixed solutions of DA and UA at different concentrations are shown; wherein Figure 7 a is MXene / Mn2O3 / Pt SA Differential pulse voltammetric response of the electrode to mixed solutions of DA and UA at different concentrations; Figure 7 b is Figure 7 The calibration curve corresponding to DA in a; Figure 7 c is Figure 7 The calibration curve corresponding to UA in b; Figure 8 Differential pulse voltammetry diagrams of mixed solutions of DA and UA at different concentrations are shown in the embodiments and comparative examples of the present invention. Detailed Implementation

[0023] To illustrate the present invention in more detail, the technical solution of the present invention will be further described below with reference to preferred embodiments and accompanying drawings.

[0024] This invention provides an MXene / Mn2O3 / Pt SA The invention relates to a composite material and its preparation method, an electrochemical sensor, and an electrochemical detection method for dopamine and / or uric acid, wherein the MXene / Mn2O3 / Pt composite material comprises a substrate, a support, and an active center, wherein the substrate is a conductive material; the support is a metal oxide; the active center is a Pt single atom; and the Pt single atom is confined within the metal oxide. The conductive material is selected from one or more of graphene, carbon nanotubes, MXene, carbon fibers, hollow carbon spheres, and reduced graphene oxide. The metal oxide precursor is selected from one or more of metal nitrates, including Co(NO3)2∙6H2O, Zn(NO3)2∙6H2O, Ni(NO3)2∙6H2O, Fe(NO3)3∙9H2O, Mn(NO3)2∙4H2O, or In(NO3)3∙xH2O. The Pt precursor is selected from one or more of chloroplatinic acid, platinum dichloride, platinum tetrachloride, sodium chloroplatinate, sodium chloroplatinate, potassium chloroplatinate, or potassium chloroplatinate.

[0025] Example 1: MXene / Mn2O3 / Pt SA Preparation and characterization of composite materials 1. Preparation process: (1) 25 mg of multilayer MXene (Ti3C2T) x The powder was dispersed in 5 mL of deionized water and magnetically stirred for 30 minutes at room temperature to obtain a uniform and stable black dispersion A.

[0026] (2) Accurately weigh 1.5061 g of manganese nitrate tetrahydrate (Mn(NO3)2·4H2O) and 10.1 mg of platinum tetrachloride (PtCl4), add them together to 5 mL of deionized water, and sonicate for 30 minutes to fully dissolve and mix the precursors to obtain dispersion B. Calculations show that the molar ratio of Pt to Mn elements at this ratio is approximately 1:100.

[0027] (3) While stirring continuously, slowly add dispersion B dropwise to dispersion A. After the addition is complete, continue stirring the mixture for 6 hours to ensure thorough mixing.

[0028] (4) Transfer the above mixture to a freeze-drying tray, pre-freeze at -20 °C for 4 hours, and then transfer it to a freeze dryer and dry it for 24 hours under a vacuum of less than 10 Pa to obtain a solid precursor.

[0029] (5) The precursor powder was transferred to an alumina ceramic boat and placed in a muffle furnace. Under air atmosphere, the temperature was programmed to rise to 250 °C at a rate of 5 °C / min, and then calcined at this temperature for 5 hours. After calcination, the furnace was allowed to cool naturally to room temperature to obtain the target product MXene / Mn2O3 / Pt. SA Black powder.

[0030] 2. Structural characterization: (1) Morphological analysis (SEM / TEM): such as Figure 1 As shown in the scanning electron microscope (SEM) image, the surface of the two-dimensional layered MXene is uniformly loaded with dense nanoparticles. Figure 2 The transmission electron microscope (TEM) image of a further confirms this morphology. Figure 2 The high-resolution TEM image of b shows that these nanoparticles have clear lattice fringes and the measured interplanar spacing is about 2.76 Å, corresponding to the (222) crystal plane of Mn2O3, which proves the successful loading of Mn2O3.

[0031] (2) Pt single-atom state analysis (HAADF-STEM): such as Figure 3As shown in the high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image, a large number of isolated, high-brightness dots can be observed (marked with circles in the image). These bright spots correspond to Pt single atoms with large atomic numbers, which intuitively proves that Pt exists in an atomically dispersed form rather than forming nanoparticles or clusters.

[0032] (3) Elemental chemical state analysis (XPS): X-ray photoelectron spectroscopy (XPS) analysis was performed on the Pt element in the composite material, and the results are as follows: Figure 4 As shown, the Pt 4f spectrum can be decomposed into two sets of doublets: the doublet with binding energies of 73.50 / 76.80 eV belongs to Pt. 2+ The bimodal pattern with binding energies of 74.85 / 77.90 eV is attributed to Pt. 4+ The spectrum did not show Pt values ​​around 71.62 / 74.9 eV. 0 Characteristic peaks were observed, which, from a chemical state perspective, ruled out the presence of metallic Pt nanoparticles. Furthermore, compared to commercial Pt / C catalysts, the Pt content in the composite material... 2+ and Pt 4+ The spectra shifted by 1.35 eV and 0.12 eV towards the direction of higher binding energy, respectively, indicating that there is a strong electronic interaction between the Pt species and the Mn2O3 support, and that the electron cloud density of Pt is reduced, indicating that it is in an electron-deficient state.

[0033] Example 2: Construction of an electrochemical sensor Take the MXene / Mn2O3 / Pt prepared in Example 1 SA 2.0 mg of the composite material was placed in a 1.5 mL centrifuge tube. 500 μL of deionized water, 490 μL of anhydrous ethanol, and 10 μL of a 5% (w / w) Nafion solution (a mixture of water and alcohol) were added sequentially. The mixture was sonicated for 10 minutes until a uniform and stable black suspension was formed, thus obtaining the modified ink. In the modified ink, the volume fraction of Nafion was 1% to 10%, the volume fraction of deionized water was 30% to 80%, and the volume fraction of anhydrous ethanol was 40% to 70%. The concentration of the Pt single-atom composite material in the modified ink was 0.1 mg / mL to 5 mg / mL.

[0034] Using a micropipette, 5 to 10 μL of the modified ink, preferably 8 μL, is vertically drop-dropped onto the polished and cleaned surface of a 3 mm diameter glassy carbon electrode (GCE), ensuring complete coverage of the electrode's working surface. The electrode is then allowed to air dry at room temperature for 12 hours until the solvent has completely evaporated, thus obtaining MXene / Mn₂O₃ / Pt. SA / GCE-modified electrode, used as the working electrode of an electrochemical sensor. Example 3: Electrochemical detection performance for dopamine (DA) The modified electrode constructed in Example 2 was used as the working electrode, the platinum wire electrode as the counter electrode, and the saturated calomel electrode (SCE) as the reference electrode, forming a three-electrode system. The electrolyte was 0.1 M phosphate buffer solution (PBS) at pH 7.4. Differential pulse voltammetry (DPV) was used for detection, with the parameters set as follows: amplitude 50 mV, pulse width 10 ms, and scan rate 50 mV / s.

[0035] The DPV method was used to test dopamine solutions with different concentration gradients (0.1-100 μM), and the results are as follows: Figure 5 As shown in figure a, a distinct and sharp DA oxidation peak appears at approximately 0.16 V (vs. SCE), and the peak current increases with increasing DA concentration. A linear fit was performed with DA concentration (C, μM) on the x-axis and the corresponding oxidation peak current (I, μA) on the y-axis, yielding a good linear relationship. Figure 5 b): I (μA) = 3.48C (μM) + 0.067 (R 2 = 0.995). Based on a signal-to-noise ratio of 3 (S / N=3), the limit of detection (LOD) for DA using this method is 3.96 nM.

[0036] Example 4: Electrochemical detection performance for uric acid (UA) The detection conditions were the same as in Example 3, except that the analyte was replaced with uric acid. In PBS at pH 7.4, the concentration of UA varied from 4 μM to 100 μM. DPV results are as follows... Figure 6 As shown in figure a, an oxidation peak of UA appears at approximately 0.29 V (vs. SCE). The peak current shows a linear relationship with UA concentration in the range of 4–100 μM. Figure 6 b): I (μA) = 0.20419C (μM) -0.57 (R 2 =0.997). The calculated detection limit for UA is 24.98 nM.

[0037] Example 5: Simultaneous detection performance of dopamine and uric acid Both DA and UA were present in PBS at pH 7.4. The concentrations of both substances were varied (5-100 μM), and DPV tests were performed. The results are as follows. Figure 7 As shown in Figure a, the oxidation peaks of DA and UA appear stably at approximately 0.16 V and 0.30 V, respectively, with a peak potential difference (ΔEp) of 140 mV. The peaks are independent, well separated, and do not interfere with each other.

[0038] Calibration curves of oxidation peak current and corresponding concentrations for DA and UA were plotted respectively. Figure 7 (b, 7c). Both exhibited good linearity within the concentration range of 5-100 μM: DA: I (μA) = 0.099C (μM) + 0.95 (R 2 = 0.999), and the LOD when coexisting is 138.18 nM.

[0039] UA: I (μA) = 0.058C (μM) + 0.624 (R 2 = 0.999), and the LOD when coexisting is 86.63 nM.

[0040] This indicates that the sensor prepared by the present invention can achieve high selectivity and high sensitivity for simultaneous detection of DA and UA.

[0041] The following is combined with Figure 8 Explain the differences between the comparative examples and the present invention: Comparative Example 1: MXene-modified electrode Except for the absence of Mn(NO3)2·4H2O and PtCl4, the preparation steps were exactly the same as in Example 1, yielding pure MXene material. The electrode was modified according to the method in Example 2. DPV tests were performed in a mixed solution containing 100 μM DA and 100 μM UA, see [link to example]. Figure 8 The results showed that the oxidation peak current response was extremely weak, indicating that pure MXene has very low catalytic activity for DA and UA.

[0042] Comparative Example 2: MXene / Pt SA Composite materials Except for omitting the addition of Mn(NO3)2·4H2O, changing the calcination atmosphere to a 10 vol% H2 / Ar mixture, the calcination temperature to 350 ℃, and the calcination time to 1 hour, the other steps were the same as in Example 1. Under these conditions, MXene supported on Pt single-atom material was obtained, denoted as MXene / Pt. SA The DPV response of its modified electrode in the same mixed solution ( Figure 8 The efficiency of Pt single atoms was significantly lower than that of Example 1, and the peak shape was wider, indicating that the lack of Mn2O3 regulation led to a decrease in the catalytic efficiency of Pt single atoms.

[0043] Comparative Example 3: MXene / Mn2O3 composite material Except for the absence of PtCl4, the other steps are exactly the same as in Example 1. The DPV response of its modified electrode ( Figure 8The results were higher than those of Comparative Example 1 but significantly lower than those of Example 1, indicating that Mn2O3 itself has certain catalytic activity, but the introduction of atomically dispersed Pt active centers can greatly improve the catalytic performance.

[0044] Performance comparison and synergistic effect analysis: The DPV response currents of Example 1 were compared with those of three comparative examples, and the results are summarized in... Figure 8 Example 1 (MXene / Mn2O3 / Pt) SA The oxidation peak currents for DA and UA are significantly higher than those of all comparative examples. This strongly demonstrates that the present invention is not a simple summation of the properties of MXene, Mn2O3, and Pt, but rather stems from the synergistic catalytic effect generated by its unique structural design. 1. The high conductivity of MXene provides a fast electron transport channel for electrochemical reactions.

[0045] 2. The Mn2O3 support not only disperses and stabilizes Pt atoms, but its strong electronic interaction with Pt atoms also regulates the electronic structure of Pt, thereby enhancing its intrinsic catalytic activity.

[0046] 3. Atomic-level dispersion of Pt maximizes the utilization of Pt atoms and provides abundant and uniform highly active sites.

[0047] The three components work synergistically to endow the composite material with excellent electrocatalytic performance, thereby achieving highly sensitive and selective detection of DA and UA (including individual and simultaneous detection).

[0048] Example 6: Application of different conductive substrate materials In step (1) of Example 1, MXene was replaced with equal masses of reduced graphene oxide (rGO) and carbon nanotubes (CNTs), while other steps remained unchanged, to prepare rGO / Mn2O3 / Pt. SA and CNTs / Mn2O3 / Pt SA Composite material. Sensors were constructed according to the methods in Examples 2 and 5 and detected in mixed solutions of DA and UA (100 μM each). The results showed that separate oxidation peaks of DA and UA could be observed in both materials, with peak current values ​​of approximately 85% and 78% of those in Example 1 (MXene substrate), respectively. This demonstrates that various highly conductive carbon materials can serve as effective substrates for this composite structure, but MXene exhibits the best overall performance due to its excellent metallic conductivity and two-dimensional layered structure. The conductive material can also be one of carbon fibers, hollow carbon spheres, or reduced graphene oxide.

[0049] Example 7: Different metal oxide precursors In step (1) of Example 1, the metal oxide precursor was replaced with one of the following metal nitrates: Co(NO3)2∙6H2O, Zn(NO3)2∙6H2O, Ni(NO3)2∙6H2O, Fe(NO3)3∙9H2O, and In(NO3)3∙xH2O; all other steps remained unchanged, and MXene / Co3O4 / Pt was prepared. SA MXene / ZnO / Pt SA MXene / NiO / Pt SA MXene / Fe2O3 / Pt SA and MXene / In2O3 / Pt SA The sensor was constructed according to the methods in Examples 2 and 5, and detection was performed using a mixed solution of DA and UA (100 μM each). The results showed that although metal oxides prepared from other metal nitrates can also modulate the catalytic performance of Pt single atoms, their catalytic ability is still slightly inferior to that of Mn2O3 prepared from manganese nitrate tetrahydrate Mn(NO3)2∙4H2O.

[0050] Example 8: Effect of buffer solutions with different pH values Using the sensor constructed in Example 2, mixed solutions containing 100 μM DA and 100 μM UA were detected in phosphate buffer solutions at pH 3.0, 5.0, 7.4, 9.0, and 11.0. The results showed that the sensor responded over a wide pH range of 3.0–11.0. With increasing pH, the oxidation peak potentials of both DA and UA shifted negatively, consistent with the characteristics of proton-mediated electrode processes. The peak separation and signal stability were optimal near pH 7.4; therefore, physiological pH is recommended as the optimal detection condition.

[0051] The following is a more detailed explanation with reference to the accompanying drawings: Figure 1 The MXene / Mn2O3 / Pt obtained in this example SA The scanning electron microscope image shows that a large number of nanoparticles are uniformly distributed on the surface of the two-dimensional sheet-like MXene, indicating the successful modification of Mn2O3.

[0052] Figure 2 The MXene / Mn2O3 / Pt obtained in this example SA The transmission electron microscope (TEM) images show that the morphological characteristics observed in TEM are consistent with those observed in scanning electron microscopy (SEM). Figure 2 a). High-resolution transmission electron microscope image ( Figure 2 Highly ordered lattice fringes can be clearly observed in b), and the lattice spacing is measured to be 2.76 Å, which is consistent with the 222 plane spacing of Mn2O3, further confirming that Mn2O3 has been successfully modified onto the MXene surface.

[0053] Figure 3 The MXene / Mn2O3 / Pt obtained in this example SA The high-angle annular dark-field scanning transmission electron microscope image clearly and intuitively demonstrates that Pt exists in the composite material in the form of single atoms, rather than nanoparticles.

[0054] Figure 4 The MXene / Mn2O3 / Pt obtained in this example SA The X-ray photoelectron spectrum of Pt clearly shows that Pt exists in the catalyst in an oxidation state above 0, which can be fitted as two sets of characteristic peaks at 73.50 / 76.80 eV and 74.85 / 77.90 eV, corresponding to Pt respectively. 2+ and Pt 4+ The chemical state of MXene / Mn2O3 / Pt is not shown, and the absence of Pt metallic orbital peaks further indicates the absence of Pt metal particles or clusters. Of particular note is the presence of Pt in the MXene / Mn2O3 / Pt chemical state. SA The entire X-ray photoelectron spectrum of Pt is shifted towards higher binding energies (compared to Pt / C). Figure 4 b) This indicates a significant electronic interaction between the Pt single atom and the Mn2O3 support, which may endow MXene / Mn2O3 / Pt with electrons. SA High catalytic activity.

[0055] Figure 5 The MXene / Mn2O3 / Pt obtained in this example SA Individual tests of dopamine solutions containing different concentration gradients revealed that the electrochemical characteristic peak of dopamine is located around 0.16 V. Figure 5 a), and the dopamine peak current showed a linear relationship with concentration, with a detection limit of 3.96 nM (a). Figure 5 b, 5c).

[0056] Figure 6 The MXene / Mn2O3 / Pt obtained in this example SA Individual tests of uric acid solutions containing different concentration gradients revealed that the electrochemical characteristic peak of uric acid was located around 0.29 V. Figure 6 a), and the peak current of uric acid showed a linear relationship with concentration, with a detection limit of 24.98 nM ( Figure 6 b, 6c).

[0057] Figure 7 The MXene / Mn2O3 / Pt obtained in this example SA Simultaneously, solutions containing different concentration gradients of dopamine and uric acid were tested. The oxidation potentials of the two were clearly separated, and the mutual interference of the current signals was minimal. Figure 7a). More importantly, their concentration changes are linearly related to the peak current ( Figure 7 (b, 7c). The detection limits for DA and UA were calculated to be 138.18 nM and 86.63 nM, respectively.

[0058] Finally, it should be noted that the above embodiments are merely preferred examples for clearly illustrating the present invention, but they are not intended to limit the implementation of the present invention. Those skilled in the art should understand that the technical features in the above solutions can be combined arbitrarily, and other modifications or equivalent substitutions can be made to some technical features based on the above specific implementation methods. It is impossible to exhaustively list all implementation methods here. Therefore, any modifications, improvements, equivalent substitutions, etc., derived from the technical solutions of the present invention within the spirit and principles of the present invention should be within the scope of protection claimed by the present invention.

Claims

1. An MXene / Mn2O3 / Pt SA Composite material, characterized in that, It includes a substrate, a support, and an active center; the substrate is a conductive material; the support is a metal oxide loaded on the substrate; the active center is an atomically dispersed Pt single atom, and the Pt single atom is confined within the metal oxide.

2. The MXene / Mn2O3 / Pt according to claim 1 SA Composite material, characterized in that, The conductive material is selected from one or more of graphene, carbon nanotubes, MXene, carbon fibers, hollow carbon spheres, and reduced graphene oxide.

3. The MXene / Mn2O3 / Pt according to claim 1 SA Composite material, characterized in that, The metal oxide precursor is selected from metal nitrates, including one or more of Co(NO3)2∙6H2O, Zn(NO3)2∙6H2O, Ni(NO3)2∙6H2O, Fe(NO3)3∙9H2O, Mn(NO3)2∙4H2O or In(NO3)3∙xH2O.

4. An MXene / Mn2O3 / Pt as described in any one of claims 1-3 SA A method for preparing composite materials, characterized in that, Includes the following steps: S1. Disperse the conductive material in deionized water and stir to obtain dispersion A; S2. The metal oxide precursor and the Pt precursor are dispersed together in deionized water and subjected to ultrasonic treatment to obtain dispersion B; wherein the molar ratio of the metal element in the metal oxide precursor to the platinum element in the Pt precursor is (50-1000):

1. S3. Mix the dispersion B with the dispersion A and stir to obtain a mixture; S4. Freeze-dry the mixture to obtain a solid precursor; S5. The solid precursor is calcined in an oxygen-containing atmosphere to obtain the MXene / Mn2O3 / Pt. SA Composite materials.

5. The preparation method according to claim 4, characterized in that: In step S2, the metal oxide precursor is a metal nitrate, and the Pt precursor is PtCl4; the molar ratio of the metal element to the platinum element is 100:

1.

6. The preparation method according to claim 5, characterized in that: The metal nitrate is manganese nitrate tetrahydrate (Mn(NO3)2∙4H2O).

7. The preparation method according to claim 4, characterized in that: In step S1, the concentration of the conductive material in deionized water is from 5 mg / mL to 50 mg / mL.

8. The preparation method according to claim 4, characterized in that: In step S5, the calcination temperature is 200-350℃, the calcination time is 1-24 hours, and the heating rate is 1-15℃ / min.

9. The preparation method according to claim 8, characterized in that: The calcination temperature is 250℃ and the calcination time is 5 hours.

10. The preparation method according to claim 4, characterized in that: In step S2, the Pt precursor is selected from one or more of chloroplatinic acid, platinum dichloride, platinum tetrachloride, sodium chloroplatinate, sodium chloroplatinate, potassium chloroplatinate, or potassium chloroplatinate.

11. The preparation method according to claim 4, characterized in that: In step S4, the freeze-drying time is 10 to 48 hours.

12. An electrochemical sensor, characterized in that, The working electrode includes a Pt single-atom composite material modified electrode, wherein the Pt single-atom composite material modified working electrode adopts the MXene / Mn2O3 / Pt as described in any one of claims 1-3. SA Composite material or MXene / Mn2O3 / Pt prepared by any one of claims 4-11 SA The modification method of the Pt single-atom composite material includes: mixing the Pt single-atom composite material with deionized water, ethanol and Nafion solution in a certain proportion to prepare a modification ink, applying the modification ink to the electrode surface, and drying it to obtain the final product.

13. The electrochemical sensor according to claim 12, characterized in that: In the modified ink, the volume fraction of Nafion is 1% to 10%, the volume fraction of deionized water is 30% to 80%, and the volume fraction of ethanol is 40% to 70%.

14. The electrochemical sensor according to claim 12, characterized in that: The concentration of Pt single-atom composite material in the modified ink is from 0.1 mg / mL to 5 mg / mL.

15. The electrochemical sensor according to claim 12, characterized in that: The amount of the modifying ink applied to the electrode is 5 μL to 10 μL.

16. An electrochemical detection method for dopamine and / or uric acid, employing the electrochemical sensor according to any one of claims 12-14, characterized in that, Includes the following steps: The working electrode of the electrochemical sensor is immersed in a phosphate buffer solution containing the analyte, and a three-electrode system is used to detect the analyte using differential pulse voltammetry to obtain a differential pulse voltammogram; the pH value of the phosphate buffer solution is 3 to 12.

17. The detection method according to claim 16, characterized in that: The analyte is dopamine, uric acid, or a mixture of both.

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