Preparation method and application of manganese tetraoxide nanomaterial with grape-like three-dimensional structure

Abstract

A method for preparing a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure and its application relates to the preparation method and application of the manganese tetraoxide nanomaterial. The present invention aims to address the problems of low purity, complex process, large particle size, uneven particle distribution, and the inability of Mn3O4 electrochemical sensors to achieve dual detection of nitrite and H2O2, which are encountered in existing Mn3O4 synthesis methods. Method: MnSO4·H2O and (NH4)2S2O8 are dissolved in a mixture of polyethylene glycol and water, followed by the addition of concentrated sulfuric acid and AgNO3 for high-temperature reaction to obtain a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure. Application: Electrodes modified with the manganese tetraoxide nanomaterial with a grape-like three-dimensional structure are used for dual detection of nitrite and H2O2. The present invention relates to a method for preparing a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure and its application.

Description

Technical Field

[0001] The invention relates to a preparation method and application of manganese manganese tetraoxide nanomaterial. Background Art

[0002] Nitrite is a nitrogen compound widely used in fertilizer and dye production. It is also an important food additive and meat colorant. Long-term or excessive consumption of meat products such as ham, pickles, leftover vegetables, canned foods, and other low-quality products with excessive nitrite levels, or drinking nitrite-contaminated water, can lead to nitrite accumulation in the body. This accelerates the irreversible conversion of hemoglobin to methemoglobin, weakening or even eliminating its oxygen-carrying capacity, ultimately causing "blue baby syndrome," which is extremely harmful to infants and young children. Nitrite can also cause diseases such as esophageal and gastric cancer. Therefore, establishing reliable analytical techniques for the rapid and sensitive detection of nitrite in food and the environment is crucial for protecting human health and the ecological environment.

[0003] H2O2 is the most common peroxide in nature, widely used in food, textiles, papermaking, pharmaceuticals, clinical practice, environmental research, and mining. Furthermore, it is a byproduct of metabolic reactions in the human body. An imbalance in H2O2 levels in the body can lead to a range of diseases, including aging, DNA damage, gene mutations, and cancer. Common conditions such as Alzheimer's disease, Parkinson's disease, stroke, arteriosclerosis, and diabetic nephropathy are also closely associated with H2O2. Therefore, accurate detection of H2O2 levels is crucial for production, daily life, and the prevention and diagnosis of certain diseases. Currently, transition metal oxides, especially manganese oxides, have become a widely used class of small molecule electrochemical sensors due to their environmental friendliness and low production cost. Mn3O4, in particular, has attracted considerable attention due to its diverse physicochemical properties and relatively stable structure. According to literature, the main methods for synthesizing Mn3O4 include catalytic oxidation of electrolytic manganese powder suspensions, calcination, and reduction.

[0004] Two methods have been reported for synthesizing quasi-spherical Mn3O4: one uses a complex precipitation method, in which a complexing agent is used to co-precipitate a manganese solution with an alkaline solution under specific conditions to obtain Mn3O4; the other uses a one-step oxidation method using manganese sulfate and ammonia as raw materials to prepare quasi-spherical Mn3O4. While both methods can produce quasi-spherical Mn3O4, they impose strict requirements on solution pH and stirring speed during the synthesis process. Furthermore, the particle size of the prepared Mn3O4 particles exceeds 10 μm, significantly reducing the specific surface area of ​​the product. For electrochemical sensing materials, a larger specific surface area provides more active sites and better electrocatalytic performance. Furthermore, a more uniform particle size distribution and higher purity also enhance sensor performance. However, all of these methods suffer from issues with purity, processing, and particle size. Furthermore, most reported electrochemical sensors for nitrite or H2O2 are single-functional, making it difficult to achieve dual detection of both substances. Therefore, it is of great practical significance and value to develop a synthesis method of Mn3O4 with high purity, small and uniform particle size distribution, and low cost and use it to develop dual electrochemical sensors for nitrite and H2O2. Summary of the Invention

[0005] The present invention aims to solve the problems of low purity, complex process, large particle size, uneven particle distribution, and the inability of Mn3O4 electrochemical sensors to achieve dual detection of nitrite and H2O2 in existing Mn3O4 synthesis methods, and further provides a preparation method and application of manganese dioxide nanomaterials with a grape-like three-dimensional structure.

[0006] A method for preparing a manganese dioxide nanomaterial having a grape-like three-dimensional structure is carried out according to the following steps:

[0007] MnSO4·H2O and (NH4)2S2O8 are dissolved in a mixture of polyethylene glycol and water and stirred to dissolve, and then concentrated sulfuric acid and AgNO3 are added and dissolved to obtain an acidic mixed solution, and the acidic mixed solution is transferred to a polytetrafluoroethylene-lined autoclave, reacted at a temperature of 100°C to 120°C for 5h to 8h, and then naturally cooled to room temperature and centrifuged to obtain a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure;

[0008] The mass ratio of the MnSO4·H2O to (NH4)2S2O8 is 1:(1-2.5); the volume ratio of the mass of the MnSO4·H2O to concentrated sulfuric acid is 1g:(3-9)mL; and the mass ratio of the MnSO4·H2O to AgNO3 is 1:(1.5-5).

[0009] Application: Electrode modification using manganese tetraoxide nanomaterials with a grape-like three-dimensional structure is used for dual detection of nitrite and H2O2.

[0010] The beneficial effects of the present invention are:

[0011] (1) The grape-shaped Mn3O4 of the present invention has high purity and uniform particle distribution, with an average particle size (500nm) much smaller than the reported spherical Mn3O4 (≥10μm). Furthermore, the Mn3O4 of the present invention also has a distinct three-dimensional structure. The small particle size and three-dimensional structure effectively increase the specific surface area of ​​Mn3O4. Furthermore, the application of Mn3O4 nanomaterial-modified electrodes for the dual detection of nitrite and H2O2 has not been reported.

[0012] (2) The material of the present invention uses a mixed solution of polyethylene glycol and water as a solvent, and synthesizes grape-shaped three-dimensional structure nanomaterials in a short time through high-temperature reaction. The synthesis method is simple and low-cost, the solvent used is environmentally friendly, and the product is easy to separate and purify, making it suitable for large-scale production.

[0013] (3) The material of the present invention has excellent electrocatalytic performance for both nitrite and H2O2. H2O2 detection: its linear range is 0.00042mmol·L -1 ~4.15mmol·L -1 , the sensitivity is 270.3μA(mmol·L -1 ) -1 cm -2 , the response time is 2.8s, and the minimum detection limit is 75nmol·L -1 ; Nitrite detection: linear range is 0.00016mmol·L -1 ~6.24mmol·L -1 , the sensitivity is 419.3μA(mmol·L -1 ) -1 cm -2 , the response time is 3.2s, and the minimum detection limit is 64nmol·L -1 , these electrochemical properties are far superior to many reported hydrogen peroxide and nitrite sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is an X-ray diffraction pattern of the manganese dioxide nanomaterial with a grape-like three-dimensional structure prepared in Example 1;

[0015] Figure 2 This is a scanning electron microscope image of the manganese dioxide nanomaterial with a grape-like three-dimensional structure prepared in Example 1;

[0016] Figure 3 The electrochemical sensor assembled by Mn3O4 / GCE prepared in Example 2 was used to measure the NO2 concentrations. - Current response curve of

[0017] Figure 4 The electrochemical sensor assembled by Mn3O4 / GCE prepared in Example 2 was used to measure the NO2 concentrations. - The linear relationship curve of

[0018] Figure 5 The current response curves of the electrochemical sensor assembled with Mn3O4 / GCE prepared in Example 2 to different concentrations of H2O2 are shown;

[0019] Figure 6 The linear relationship curve of the electrochemical sensor assembled using Mn3O4 / GCE prepared in Example 2 to different concentrations of H2O2. DETAILED DESCRIPTION

[0020] Specific embodiment 1: This embodiment is a method for preparing a manganese oxide nanomaterial with a grape-like three-dimensional structure, which is carried out according to the following steps:

[0021] MnSO4·H2O and (NH4)2S2O8 are dissolved in a mixture of polyethylene glycol and water and stirred to dissolve, and then concentrated sulfuric acid and AgNO3 are added and dissolved to obtain an acidic mixed solution, and the acidic mixed solution is transferred to a polytetrafluoroethylene-lined autoclave, reacted at a temperature of 100°C to 120°C for 5h to 8h, and then naturally cooled to room temperature and centrifuged to obtain a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure;

[0022] The mass ratio of the MnSO4·H2O to (NH4)2S2O8 is 1:(1-2.5); the volume ratio of the mass of the MnSO4·H2O to concentrated sulfuric acid is 1g:(3-9)mL; and the mass ratio of the MnSO4·H2O to AgNO3 is 1:(1.5-5).

[0023] The beneficial effects of this embodiment are:

[0024] (1) The grape-shaped Mn3O4 in this embodiment has high purity and uniform particle distribution, with an average particle size (500 nm) much smaller than the reported spherical Mn3O4 (≥10 μm). Furthermore, the Mn3O4 in this embodiment also has a distinct three-dimensional structure. The small particle size and three-dimensional structure effectively increase the specific surface area of ​​the Mn3O4. Furthermore, the application of Mn3O4 nanomaterial-modified electrodes for dual detection of nitrite and H2O2 has not been reported.

[0025] (2) The material of this embodiment uses a mixed solution of polyethylene glycol and water as a solvent, and synthesizes grape-shaped three-dimensional structure nanomaterials in a short time by high-temperature reaction. The synthesis method is simple and low-cost, the solvent used is environmentally friendly, and the product is easy to separate and purify, which is suitable for large-scale production.

[0026] (3) The material of this embodiment has excellent electrocatalytic performance for both nitrite and H2O2. H2O2 detection: its linear range is 0.00042mmol·L -1 ~4.15mmol·L -1 , the sensitivity is 270.3μA(mmol·L -1 ) -1 cm -2 , the response time is 2.8s, and the minimum detection limit is 75nmol·L -1 ; Nitrite detection: linear range is 0.00016mmol·L -1 ~6.24mmol·L -1 , the sensitivity is 419.3μA(mmol·L -1 ) -1 cm -2 , the response time is 3.2s, and the minimum detection limit is 64nmol·L -1 , these electrochemical properties are far superior to many reported hydrogen peroxide and nitrite sensors.

[0027] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the volume ratio of polyethylene glycol to water in the polyethylene glycol and water mixture is 1:(2-4). Other aspects are the same as specific embodiment 1.

[0028] Specific embodiment 3: This embodiment differs from either specific embodiment 1 or 2 in that the volume ratio of the total mass of the MnSO4·H2O and (NH4)2S2O8 to the mixed solution of polyethylene glycol and water is 1g:(50-70)mL. Other aspects are the same as specific embodiments 1 or 2.

[0029] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the mass percentage of the concentrated sulfuric acid is 95% to 98%. Other aspects are the same as specific embodiments 1 to 3.

[0030] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the centrifugal separation is carried out at a rotation speed of 6000 to 8000 rpm for 3 to 5 minutes. Other aspects are the same as specific embodiments 1 to 4.

[0031] Specific embodiment 6: This embodiment uses manganese dioxide nanomaterials with a grape-like three-dimensional structure to modify electrodes for dual detection of nitrite and H2O2.

[0032] Specific embodiment seven: This embodiment differs from specific embodiment six in that the electrode modification using manganese oxide nanomaterials having a grape-like three-dimensional structure is specifically carried out in the following steps:

[0033] Anhydrous ethanol is added to the manganese tetraoxide nanomaterial having a grape-like three-dimensional structure and uniformly dispersed to obtain a mixed solution. The mixed solution is drop-coated onto the polished and activated electrode surface and then air-dried. Finally, a chitosan solution is drop-coated onto the electrode surface and air-dried to obtain an electrode modified with the manganese tetraoxide nanomaterial having a grape-like three-dimensional structure. The remaining steps are the same as those in Specific Embodiment 6.

[0034] Specific embodiment eight: This embodiment differs from specific embodiment six or seven in that the concentration of the manganese oxide nanomaterial with a grape-like three-dimensional structure in the mixed solution is 1 mg / mL to 3 mg / mL. Other aspects are the same as specific embodiment six or seven.

[0035] Specific embodiment 9: This embodiment differs from any one of specific embodiments 6 to 8 in that the polished and activated electrode is specifically processed according to the following steps: the electrode is polished using aluminum oxide powder with a particle size of 1.0 μm to 0.05 μm, then ultrasonically cleaned using 40% to 50% by mass nitric acid, anhydrous ethanol, and ultrapure water, and finally, the cleaned electrode is placed in a sulfuric acid solution with a concentration of 0.2 mol / L to 0.3 mol / L and cyclic voltammetry activated at a voltammetric scanning potential range of -1.0 V to 1.0 V, with a scanning number of 15 to 30 cycles. Other aspects are the same as specific embodiments 6 to 8.

[0036] Specific embodiment 10: This embodiment differs from any one of specific embodiments 6 to 9 in that the coating amount is 0.02 mg / cm 2 ~0.07mg / cm 2 , drop the mixed solution onto the polished and activated electrode surface; the drop amount is 0.03 mg / cm 2 ~0.2mg / cm 2 , dropwise add chitosan solution with a mass percentage of 0.2% to 0.5% onto the electrode surface and air dry. Other steps are the same as those in specific embodiments 6 to 9.

[0037] The following examples are used to verify the beneficial effects of the present invention:

[0038] Example 1:

[0039] A method for preparing a manganese dioxide nanomaterial having a grape-like three-dimensional structure is carried out according to the following steps:

[0040] 0.27 g of MnSO4·H2O and 0.37 g of (NH4)2S2O8 were dissolved in a mixture of 40 mL of polyethylene glycol and water and stirred to dissolve. 1.6 mL of concentrated sulfuric acid and 0.8 g of AgNO3 were then added and dissolved to obtain an acidic mixed solution. The acidic mixed solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 120°C for 6 h. The mixture was then naturally cooled to room temperature and centrifuged to obtain a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure.

[0041] The volume ratio of polyethylene glycol to water in the mixture of polyethylene glycol and water is 1:3;

[0042] The mass percentage of the concentrated sulfuric acid is 98%.

[0043] The centrifugal separation is specifically carried out at a rotation speed of 8000 rpm for 5 minutes.

[0044] Example 2: An application of a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure, wherein the manganese tetraoxide nanomaterial with a grape-like three-dimensional structure is used to modify an electrode for dual detection of nitrite and H2O2.

[0045] The electrode modification using the manganese oxide nanomaterial with a grape-like three-dimensional structure is specifically carried out in the following steps:

[0046] Anhydrous ethanol was added to the manganese tetraoxide nanomaterial with a grape-like three-dimensional structure and dispersed evenly to obtain a mixed solution. The coating amount was 0.06 mg / cm 2 The mixed solution was dropped onto the polished and activated glassy carbon electrode surface, and then dried in air. Finally, the drop amount was 0.1 mg / cm 2 , a chitosan solution with a mass percentage of 0.2% was added dropwise to the surface of a glassy carbon electrode and air-dried to obtain an electrode modified with manganese tetraoxide nanomaterials having a grape-like three-dimensional structure (Mn3O4 / GCE);

[0047] The concentration of the manganese tetraoxide nanomaterial having a grape-like three-dimensional structure in the mixed solution is 2 mg / mL;

[0048] The polished and activated glassy carbon electrode is specifically prepared according to the following steps: the glassy carbon electrode is polished with aluminum oxide powder with particle sizes of 1.0 μm, 0.3 μm and 0.05 μm, respectively, and then ultrasonically cleaned for 3 minutes at a power of 60 W using 50% by mass nitric acid, anhydrous ethanol and ultrapure water, respectively. Finally, the cleaned glassy carbon electrode is placed in a sulfuric acid solution with a concentration of 0.25 mol / L, and cyclic voltammetry activation is performed under the condition of a voltammetric scanning potential range of -1.0 V to 1.0 V, with a scanning number of 20 circles.

[0049] Figure 1 This is the X-ray diffraction pattern of the manganese oxide nanomaterial with a grape-like three-dimensional structure prepared in Example 1. As can be seen from the figure, no diffraction peaks of any other substances appear, indicating that the Mn3O4 prepared by this method is of high purity.

[0050] Figure 2 This is a scanning electron microscope image of the manganese oxide nanomaterial with a grape-like three-dimensional structure prepared in Example 1; as can be seen from the figure, the Mn3O4 nanomaterial forms a uniformly distributed grape-like three-dimensional structure, the average size of the grape-shaped Mn3O4 particles is 500nm, and the grape balls are connected by branches with an average thickness of 100nm.

[0051] The electrode modified with the grape-like three-dimensional structure manganese oxide nanomaterial prepared in Example 2 was assembled into an electrochemical sensor, and its electrocatalytic performance was tested:

[0052] Electrocatalytic performance test of nitrite and H2O2: The H2O2 concentration needs to be calibrated before the test. During the test, the three-electrode system (working electrode - Mn3O4 / GCE; reference electrode - Ag / AgCl electrode; auxiliary electrode - platinum mesh electrode) was placed in a continuously stirred 50mL phosphate buffer solution (0.05mol·L -1 ) in the electrolytic cell, set the applied potential (NO2 - The detection potential is 0.9V, the detection potential of H2O2 is -0.4V) and the appropriate running time, select a micro-injector with an appropriate range to quickly inject nitrite or H2O2 sample into the electrolytic cell, observe the response current change, and add the next sample solution after a platform appears. - The detection concentration range is 0.00016mmol·L -1 ~6.24mmol·L -1 The detection range of H2O2 concentration is 0.00042mmol·L -1 ~4.15mmol·L -1All tests were conducted at room temperature (25°C). The sensitivity in this example is the rate of change of the current response per unit area relative to the nitrite or H2O2 concentration. The response time corresponds to the time from the addition of the nitrite or H2O2 sample to the current reaching 90% of the maximum response current.

[0053] Figure 3 The electrochemical sensor assembled by Mn3O4 / GCE prepared in Example 2 was used to measure the NO2 concentrations. - Current response curve. Figure 4 The electrochemical sensor assembled by Mn3O4 / GCE prepared in Example 2 was used to measure the NO2 concentrations. - The linear relationship curve of the sensor is shown in the figure. - It exhibits very good electrocatalytic performance; at an applied potential of 0.9 V, the sensor has a high sensitivity to NO2 - The response time is 3.2s, at 0.00016mmol·L -1 ~6.24mmol·L -1 Within the concentration range, the response current and NO2 - There is a good linear relationship between the concentrations (fitting coefficient R 2 =0.9989), the sensitivity is 419.3μA(mmol·L -1 ) -1 cm -2 The minimum detection limit was 64 nmol·L -1 .

[0054] Figure 5 The current response curves of the electrochemical sensor assembled using Mn3O4 / GCE prepared in Example 2 to different concentrations of H2O2 are shown. Figure 6 The linear relationship curve of the electrochemical sensor assembled with Mn3O4 / GCE prepared in Example 2 to different concentrations of H2O2 is shown in the figure. As can be seen from the figure, the sensor exhibits very good electrocatalytic performance to H2O2; the response time to H2O2 at an applied potential of -0.4V is 2.8s, and the response time at 0.00042mmol·L -1 ~4.15mmol·L -1 Within the concentration range, there is a good linear relationship between the response current and the H2O2 concentration (fitting coefficient R 2 =0.9991), with a sensitivity of 270.3 μA (mmol·L -1 ) -1 cm -2 The minimum detection limit is 75 nmol·L -1 .

Claims

1. A method for preparing a manganese tetraoxide nanomaterial having a grape-like three-dimensional structure, characterized in that It is carried out in the following steps: MnSO4·H2O and (NH4)2S2O8 are dissolved in a mixture of polyethylene glycol and water and stirred to dissolve, and then concentrated sulfuric acid and AgNO3 are added and dissolved to obtain an acidic mixed solution, and the acidic mixed solution is transferred to a polytetrafluoroethylene-lined autoclave, reacted at a temperature of 100°C to 120°C for 5h to 8h, and then naturally cooled to room temperature and centrifuged to obtain a manganese tetraoxide nanomaterial with a grape-like three-dimensional structure; The mass ratio of the MnSO4·H2O to (NH4)2S2O8 is 1:(1-2.5); the volume ratio of the mass of the MnSO4·H2O to concentrated sulfuric acid is 1g:(3-9)mL; and the mass ratio of the MnSO4·H2O to AgNO3 is 1:(1.5-5).

2. The method for preparing a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 1, characterized in that The volume ratio of polyethylene glycol to water in the mixed solution of polyethylene glycol and water is 1:(2-4).

3. The method for preparing a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 1, characterized in that The volume ratio of the total mass of the MnSO4·H2O and (NH4)2S2O8 to the mixed solution of polyethylene glycol and water is 1g:(50-70)mL.

4. The method for preparing a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 1, characterized in that The mass percentage of the concentrated sulfuric acid is 95% to 98%.

5. The method for preparing a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 1, characterized in that The centrifugal separation is specifically carried out at a rotation speed of 6000 rpm to 8000 rpm for 3 min to 5 min.

6. The use of a manganese dioxide nanomaterial having a grape-like three-dimensional structure as claimed in claim 1, characterized in that Electrode modification using manganese tetraoxide nanomaterials with a grape-like three-dimensional structure was used for the dual detection of nitrite and H2O2.

7. The use of a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 6, characterized in that The electrode modification using the manganese oxide nanomaterial with a grape-like three-dimensional structure is specifically carried out in the following steps: Anhydrous ethanol is added to the manganese tetraoxide nanomaterial with a grape-like three-dimensional structure and dispersed evenly to obtain a mixed solution. The mixed solution is drop-coated on the polished and activated electrode surface and then dried in air. Finally, a chitosan solution is drop-coated on the electrode surface and air-dried to obtain an electrode modified with the manganese tetraoxide nanomaterial with a grape-like three-dimensional structure.

8. The use of a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 7, characterized in that The concentration of the manganese tetraoxide nanomaterial with a grape-like three-dimensional structure in the mixed solution is 1 mg / mL to 3 mg / mL.

9. The use of a manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 7, characterized in that The polished and activated electrode is specifically processed according to the following steps: the electrode is polished using aluminum oxide powder with a particle size of 1.0μm to 0.05μm, and then ultrasonically cleaned using nitric acid, anhydrous ethanol and ultrapure water with a mass percentage of 40% to 50%. Finally, the cleaned electrode is placed in a sulfuric acid solution with a concentration of 0.2mol / L to 0.3mol / L, and cyclic voltammetry activation is performed under the condition of a voltammetric scanning potential range of -1.0V to 1.0V, with the number of scanning cycles being 15 to 30 cycles.

10. The use of the manganese dioxide nanomaterial having a grape-like three-dimensional structure according to claim 7, characterized in that The coating amount is 0.02mg / cm 2 ~0.07mg / cm 2 , drop the mixed solution onto the polished and activated electrode surface; the drop amount is 0.03 mg / cm 2 ~0.2mg / cm 2 , chitosan solution with a mass percentage of 0.2% to 0.5% is added dropwise to the electrode surface and air-dried.

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