Preparation method of flower cluster-shaped silver vanadate nanoszyme based on silver ammine solution as precursor

Abstract

The application discloses a preparation method of flower cluster-shaped silver vanadate nanoscale enzyme based on silver ammine solution as a precursor, relates to the technical field of chemical detection, and develops a nanoscale enzyme colorimetric sensing method for detecting EGCG based on the promotion effect of epigallocatechin gallate (EGCG) on TMB oxidation. As a preliminary exploration of the "off-on" mode sensing polyphenol based on nanoscale enzyme, the idea of synthesizing artificial nanoscale enzyme is proposed from the perspective of material, and the most advanced colorimetric sensing strategy for polyphenols other than EGCG is displayed. The method prepares flower cluster-shaped Ag3VO4 nanoscale enzyme through the way of coprecipitation, and realizes the colorimetric quantitative detection of natural or artificially synthesized polyphenols with specific structures through the signal "off-on" mode instead of the traditional "on-off" mode, so that the problems of high material background noise, insufficient signal resolution and disadvantage for naked eye observation are solved.

Description

Technical Field

[0001] This invention relates to the field of chemical detection technology, specifically to a method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor. Background Technology

[0002] Polyphenols, collectively known as polyhydroxy natural compounds, are important secondary metabolites, mainly classified into flavonoids, tannins, anthocyanins, and phenolic acids, possessing excellent antioxidant properties. Scientists have discovered that some polyphenols (such as grape polyphenols) have anti-inflammatory and anti-cancer effects and can treat diabetes, playing a vital role in health. Therefore, developing simpler and more effective methods for the quantitative detection of polyphenols is of great significance. To date, the detection of polyphenolic compounds primarily relies on instrumental analysis methods such as electrochemical methods, chromatography, nuclear magnetic resonance, and microfluidics. The drawbacks are that simple methods like electrochemical methods struggle to differentiate the potentials of multiple components in complex samples, while large-scale instruments like chromatography are complex and expensive. Therefore, it is necessary to develop a simple and sensitive chemical detection method for polyphenols, which has significant research implications for fields such as medicine and chemistry.

[0003] Nanozymes are a class of nanomaterials with enzyme-like catalytic activity, with dimensions less than 100 nm. Compared to natural enzymes, nanozymes are more diverse, and their activity and reaction mechanisms can be selected and optimized through artificial design and control of parameters such as composition, nanostructure, and reaction environment, thereby meeting the application requirements of different systems. Vanadium (V) is a metallic element with variable oxidation states, a property that endows its oxides with unique properties and great application value, especially ternary metal vanadates, which are a new type of multifunctional material. It has been reported that V₂O₅ nanowires exhibit significant peroxidase-like activity in the presence of hydrogen peroxide, with vanadium ions serving as the catalytic active center. Studying the mechanism of nanozyme oxidase-like activity to obtain higher performance is of paramount importance for biosensing and biocatalysis. Given the advantages of metal-based artificial nanozymes, such as excellent enzyme-like activity, high stability, and good biocompatibility, we synthesized a physicochemically stable, cluster-shaped silver vanadate nanozyme using a solution co-precipitation method and precise control of reaction conditions. This nanozyme exhibited good oxidase-like activity against the substrate TMB. Furthermore, the study revealed that artificial nanozymes exhibit highly sensitive response to polyhydroxy compounds.

[0004] Currently, reported colorimetric detection techniques for reducing organic / biomolecule small molecules using nanozymes as core catalysts generally employ an "on-off" signal expression mode when reactive oxygen species act as electron acceptors. Compared to the "on-off" mode, analytical detection systems expressing sensing behavior using an "off-on" signal enhancement mode offer advantages such as low background noise and high detection signal resolution, representing the optimal approach sought after in the fields of materials and chemical sensors. Based on the technical challenges encountered in the analysis and detection of polyphenolic compounds using existing materials and methods, and considering the objective scientific and technological needs of current socio-economic development, this invention describes a method for preparing flower cluster-shaped Ag3VO4 nanozymes using silver ammonia solution as a precursor via co-precipitation. This method develops a quantitative analysis method for polyphenolic compounds in complex samples using an enhanced "off-on" signal mode, providing positive technical support for the development of nanozyme materials and analytical chemistry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing flower-like silver vanadate nanozymes based on silver ammonia solution as a precursor, comprising the following steps:

[0007] S1. Preparation of silver ammonia solution: Based on silver nitrate solution and sodium hydroxide solution, the prepared silver ammonia solution is used as a precursor;

[0008] S2. Preparation of α-Ag3VO4 nanozyme without the addition of sodium nitrate;

[0009] S3. Preparation of α-Ag3VO4 nanozyme with added sodium nitrate;

[0010] S4. Detect the presence or absence of sodium nitrate in the two types of α-Ag3VO4 nanozymes;

[0011] S5. Detect the oxidase activity of α-Ag3VO4 with added sodium nitrate;

[0012] S6. Using α-Ag3VO4 with added sodium nitrate, gallocatechin gallate (EGCG) was quantitatively detected colorimetrically in a signal-enhanced "off-on" mode.

[0013] To further optimize this technical solution, step S1, the preparation of the silver ammonia solution, includes the following specific process:

[0014] Weigh 4.25g of silver nitrate solid and add it to a 100ml beaker. Then add 50ml of deionized water to the beaker to completely dissolve the silver nitrate and prepare a 0.5mol / L silver nitrate solution, which is called solution A.

[0015] Weigh 0.2g of sodium hydroxide solid and add it to 100ml of deionized water in a 250ml beaker. Stir until completely dissolved to obtain a 0.05mol / L sodium hydroxide solution, which is used as solution B.

[0016] Slowly add solution B to solution A while stirring continuously, and a brown precipitate will form;

[0017] Measure 1.25 ml of concentrated ammonia solution and add it to a 50 ml beaker. Then add 30 ml of deionized water to the beaker to prepare dilute ammonia solution.

[0018] Slowly add dilute ammonia solution dropwise into the brown precipitate while stirring continuously until the precipitate just disappears. The resulting solution is a silver ammonia solution.

[0019] To further optimize this technical solution, step S2, the preparation of α-Ag3VO4 nanozyme without the addition of sodium nitrate includes the following specific process:

[0020] Take a 100ml beaker, add 2.92g of ammonium metavanadate solid to the beaker, then measure 50ml of deionized water and add it to the beaker. Stir at room temperature to dissolve it completely, and you will get a 0.5mol / L NH4VO3 solution.

[0021] Silver ammonia solution and NH4VO3 solution were added dropwise at a mass ratio of 1:1, stirred thoroughly, and then placed in a reaction vessel and reacted at 80°C for 24 hours.

[0022] After the reaction is complete, cool to room temperature, pour the obtained solid into a centrifuge tube and centrifuge at high speed. The centrifugation rate is set to 8000 r per minute and the centrifugation time is set to 5 min.

[0023] The solid was washed, and after washing, the product was placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain α-Ag3VO4 nanozyme without sodium nitrate.

[0024] To further optimize this technical solution, the solid is first centrifuged three times with deionized water and then centrifuged three times with anhydrous ethanol during washing to complete the washing process.

[0025] To further optimize this technical solution, step S3, the preparation of α-Ag3VO4 nanozyme with added sodium nitrate, includes the following specific process:

[0026] Weigh out two portions of 2.125g NaNO3, add one portion to the silver ammonia solution used as a precursor, and stir thoroughly to obtain a silver ammonia-sodium nitrate solution;

[0027] Take a 100ml beaker, add 2.92g of ammonium metavanadate solid to the beaker, then measure 50ml of deionized water and add it to the beaker. Stir at room temperature to dissolve it completely, and you will get a 0.5mol / L NH4VO3 solution.

[0028] Add another portion of NaNO3 to the NH4VO3 solution and stir until homogeneous to obtain an NH4VO3-NaNO3 solution;

[0029] The prepared silver ammonia-sodium nitrate solution and NH4VO3-NaNO3 solution were added dropwise at a mass ratio of 1:1. After thorough stirring, the mixture was placed in a reaction vessel and reacted at 80°C for 24 hours.

[0030] After the reaction is complete, cool to room temperature, pour the obtained solid into a centrifuge tube and centrifuge at high speed. The centrifugation rate is set to 8000 r per minute and the centrifugation time is set to 5 min.

[0031] The solid was washed, and after washing, the product was placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain α-Ag3VO4 nanozyme with added sodium nitrate.

[0032] To further optimize this technical solution, in step S4, based on the field emission scanning electron microscope (SEM) measurement results, flower cluster-shaped α-Ag3VO4 nanozymes are selected;

[0033] Field emission scanning electron microscopy (SEM) measurements showed that the synthesized α-Ag3VO4 with added NaNO3 had a flower-like morphology with distinct shapes and no other impurities or particles. In contrast, the α-Ag3VO4 without added NaNO3 also showed a flower-like morphology, but the particles were not as distinct.

[0034] To further optimize this technical solution, step S5 includes the following specific steps for detection:

[0035] With a total reaction volume of 3 mL, 0.04 mg / mL of α-Ag3VO4 solution was added to NaAc-HAc buffer solution with a pH of 4, shaken well, and then 0.15 mmol / L of TMB solution was added. The mixture was stirred evenly and reacted at room temperature for 31 min.

[0036] To further optimize this technical solution, the preparation processes of the TMB solution and the α-Ag3VO4 solution respectively include the following:

[0037] TMB solution: At room temperature, add 7.2 mg of TMB powder to 2 mL of anhydrous ethanol. After complete dissolution, store the solution in a refrigerator at 4°C away from light for later use.

[0038] For the α-Ag3VO4 solution, measure 2 mL of H2O, disperse 6 mg of silver vanadate powder in it, and sonicate at room temperature for 30 min until evenly dispersed. In subsequent experiments, shake well before use.

[0039] Compared with the prior art, the present invention provides a method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor, which has the following beneficial effects:

[0040] This method for preparing flower-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor prepares flower-shaped Ag3VO4 nanozymes through co-precipitation. It achieves colorimetric quantitative detection of natural or artificially synthesized polyphenolic compounds with specific structures by using a signal "off-on" mode instead of the traditional "on-off" mode, thus solving problems such as high background noise, insufficient signal resolution, and difficulty in visual observation. Attached Figure Description

[0041] Figure 1 SEM image of the α-Ag3VO4 nanozyme prepared in the embodiments of the present invention;

[0042] Figure 2 The XRD powder diffraction pattern of the α-Ag3VO4 nanozyme prepared in the embodiments of the present invention;

[0043] Figure 3 Infrared spectrum of α-Ag3VO4 nanozyme prepared in an embodiment of the present invention;

[0044] Figure 4 The ultraviolet absorption spectra of α-Ag3VO4+TMB and α-Ag3VO4+TMB+H2O2 prepared in the embodiments of the present invention;

[0045] Figure 5 Cyclic voltammetry curves of α-Ag3VO4+TMB prepared for embodiments of the present invention;

[0046] Figure 6 This is a comparison diagram of different free radical scavengers of α-Ag3VO4+TMB prepared in the embodiments of the present invention.

[0047] Figure 7 The V 2p XPS spectrum of α-Ag3VO4 prepared in an embodiment of the present invention;

[0048] Figure 8 The O 1s XPS spectrum of α-Ag3VO4 prepared in an embodiment of the present invention;

[0049] Figure 9 EPR image of α-Ag3VO4+TMB+EGCG prepared in an embodiment of the present invention;

[0050] Figure 10 The working curves of α-Ag3VO4 and TMB at different concentrations of EGCG at 652 nm are prepared for embodiments of the present invention.

[0051] Figure 11 The UV absorption spectra of α-Ag3VO4 and TMB at different concentrations of EGCG at 652 nm, prepared for embodiments of the present invention;

[0052] Figure 12 This is a schematic diagram of the oxidation reaction of TMB in an embodiment of the present invention;

[0053] Figure 13 This is a schematic diagram of the reaction process for preparing silver ammonia solution in an embodiment of the present invention;

[0054] Figure 14 This is a schematic diagram of the reaction process of the two types of silver vanadates in the presence or absence of sodium nitrate. Detailed Implementation

[0055] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] Example:

[0057] A method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor includes the following steps:

[0058] S1. Preparation of silver ammonia solution: Based on silver nitrate solution, sodium hydroxide solution and ammonia solution, the prepared silver ammonia solution is used as a precursor.

[0059] Among them, such as Figure 13 As shown, the preparation of silver ammonia solution includes the following specific steps:

[0060] Weigh 4.25g of silver nitrate solid and add it to a 100ml beaker. Then add 50ml of deionized water to the beaker to completely dissolve the silver nitrate and prepare a 0.5mol / L silver nitrate solution, which is called solution A.

[0061] Weigh 0.2g of sodium hydroxide solid and add it to 100ml of deionized water in a 250ml beaker. Stir until completely dissolved to obtain a 0.05mol / L sodium hydroxide solution, which is used as solution B.

[0062] Slowly add solution B to solution A while stirring continuously, and a brown precipitate will form;

[0063] Measure 1.25 ml of concentrated ammonia solution and add it to a 50 ml beaker. Then add 30 ml of deionized water to the beaker to prepare dilute ammonia solution.

[0064] Slowly add dilute ammonia solution dropwise into the brown precipitate while stirring continuously until the precipitate just disappears. The resulting solution is a silver ammonia solution.

[0065] S2, such as Figure 14 As shown, α-Ag3VO4 nanozymes without the addition of sodium nitrate were prepared.

[0066] The preparation of α-Ag3VO4 nanozymes without the addition of sodium nitrate includes the following specific steps:

[0067] Take a 100ml beaker, add 2.92g of ammonium metavanadate solid to the beaker, then measure 50ml of deionized water and add it to the beaker. Stir at room temperature to dissolve it completely, and you will get a 0.5mol / L NH4VO3 solution.

[0068] Silver ammonia solution and NH4VO3 solution were added dropwise at a mass ratio of 1:1, stirred thoroughly, and then placed in a reaction vessel and reacted at 80°C for 24 hours.

[0069] After the reaction is complete, cool to room temperature, pour the obtained solid into a centrifuge tube and centrifuge at high speed. The centrifugation rate is set to 8000 r per minute and the centrifugation time is set to 5 min.

[0070] The solid was washed by first centrifuging three times with deionized water and then three times with anhydrous ethanol. After washing, the product was placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain α-Ag3VO4 nanozyme without sodium nitrate.

[0071] S3. Preparation of α-Ag3VO4 nanozymes with added sodium nitrate.

[0072] The preparation of α-Ag3VO4 nanozymes with added sodium nitrate includes the following specific steps:

[0073] Weigh out two portions of 2.125g NaNO3, add one portion to the silver ammonia solution used as a precursor, and stir thoroughly to obtain a silver ammonia-sodium nitrate solution;

[0074] Take a 100ml beaker, add 2.92g of ammonium metavanadate solid to the beaker, then measure 50ml of deionized water and add it to the beaker. Stir at room temperature to dissolve it completely, and you will get a 0.5mol / L NH4VO3 solution.

[0075] Add another portion of NaNO3 to the NH4VO3 solution and stir until homogeneous to obtain an NH4VO3-NaNO3 solution;

[0076] The prepared silver ammonia-sodium nitrate solution and NH4VO3-NaNO3 solution were added dropwise at a mass ratio of 1:1. After thorough stirring, the mixture was placed in a reaction vessel and reacted at 80°C for 24 hours.

[0077] After the reaction is complete, cool to room temperature, pour the obtained solid into a centrifuge tube and centrifuge at high speed. The centrifugation rate is set to 8000 r per minute and the centrifugation time is set to 5 min.

[0078] The solid was washed, and after washing, the product was placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain α-Ag3VO4 nanozyme with added sodium nitrate.

[0079] S4. Characterize the two α-Ag3VO4 nanozymes with and without sodium nitrate.

[0080] Based on field emission scanning electron microscopy (SEM) measurements, α-Ag3VO4 nanozymes with a flower cluster shape were selected.

[0081] exist Figure 1 In the assay, field emission scanning electron microscopy (SEM) measurements showed that the synthesized α-Ag3VO4 with added NaNO3 exhibited a flower-like morphology with distinct shapes and no other impurities or particles. While the α-Ag3VO4 without added NaNO3 also showed a flower-like morphology, the particles were less distinct. Figure 2 The XRD pattern of the silver vanadate nanozyme shows that α-silver vanadate has good crystallinity, exhibiting strong diffraction peaks on the (011), (−121), (121), (220), (301), (400), and (−213) crystal planes, indicating that the nanozyme exists in a monoclinic phase. In the infrared spectrum (e.g., ... Figure 3 (As shown), 1654cm -1 and 3439cm -1 The peaks at 704 and 923 cm⁻¹ correspond to the stretching vibration of OH, indicating the presence of a large amount of adsorbed water (oxygen) on the sample surface. -1 The absorption peak at that point represents the VO4+ in silver vanadate. - The V-O-V characteristic stretching vibration of ions.

[0082] Unless otherwise specified, α-Ag3VO4 refers to silver vanadate nanozyme with added sodium nitrate.

[0083] S5. Detect the oxidase activity of α-Ag3VO4 with added sodium nitrate.

[0084] The testing process includes the following specific steps:

[0085] With a total reaction volume of 3 mL, 0.04 mg / mL of α-Ag3VO4 solution was added to NaAc-HAc buffer solution with a pH of 4, shaken well, and then 0.15 mmol / L of TMB solution was added and mixed thoroughly. The mixture was then allowed to react at room temperature for 31 min.

[0086] The preparation processes for the TMB solution and the α-Ag3VO4 solution include the following:

[0087] TMB solution: At room temperature, add 7.2 mg of TMB powder to 2 mL of anhydrous ethanol. After complete dissolution, store the solution in a refrigerator at 4 ℃ away from light for later use.

[0088] For the α-Ag3VO4 solution, measure 2 mL of H2O, disperse 6 mg of silver vanadate powder in it, and sonicate at room temperature for 30 min until evenly dispersed. In subsequent experiments, shake well before use.

[0089] We used TMB as a chromogenic agent to test the oxidase-like activity of α-Ag3VO4 in a NaAc-HAc buffer solution at pH 4. As shown in Figure 4, upon addition of α-Ag3VO4 to the colorless TMB solution, it immediately converted to a blue oxidized state (OxTMB), exhibiting an absorption peak at approximately 652 nm. The presence of H2O2 in the α-Ag3VO4 + TMB system did not accelerate the oxidation of TMB, demonstrating that the prepared α-Ag3VO4 only possesses oxidase-like activity. Figure 5 As shown in the cyclic voltammetry, compared with the pure Ag3VO4 system, the Ag3VO4+ TMB system exhibited a significant redox current, indicating that a redox reaction occurred, confirming that effective charge transfer and exchange can occur between α-Ag3VO4 and TMB.

[0090] We optimized the catalytic efficiency: since the rate of interfacial catalytic reaction is controlled by the active sites on the catalyst and the concentration of reactants in the solution, the reaction efficiency is significantly improved with increasing concentrations of α-Ag3VO4 (5-80µg) or TMB (0.025-0.4mM).

[0091] The optimal pH for this reaction is 4. At pH 2-3, lower pH values ​​may lead to two-electron oxidation, causing the color of Ox TMB to change from light blue to yellow. At higher pH values ​​(5-6), the catalyst loses almost all its efficiency. The material carries a negative charge at pH 4, which may enhance the electrostatic interaction between the catalyst and the positively charged substrate, thereby promoting charge transfer and improving catalytic efficiency.

[0092] Similar to natural enzymes, nanozymes also exhibit temperature-dependent activity. We found that temperature has a decisive influence on the activity of α-Ag3VO4, which retains some activity at 5°C, indicating superior enzymatic activity at low temperatures. This activity reaches its maximum at 25°C and rapidly declines with further increases in temperature. Based on these results, unless otherwise stated, the following experiments were conducted at pH 4 and 25°C.

[0093] To explore the major reactive oxygen species (ROSs) in the α-Ag3VO4 enzymatic reaction, p-benzoquinone (PBQ), sodium azide (NaN3), and butanol (TBA) were added to the α-Ag3VO4 + TMB system as superoxide radicals (O2·). − Singlet oxygen () 1 Specific probes for O2) and hydroxyl radicals (·OH). Figure 6 The results showed that PBO and NaN3 both inhibited the oxidation of TMB, while TBA had no significant effect. This indicates that no hydroxyl radicals were involved in the enzyme-like catalytic reaction of silver vanadate nanozymes, but superoxide radicals and singlet oxygen played a key role.

[0094] S6. Using α-Ag3VO4 with added sodium nitrate, gallocatechin gallate (EGCG) was quantitatively detected colorimetrically in a signal-enhanced "off-on" mode.

[0095] To explore the α-Ag3VO4+ TMB system, a colorimetric platform for sensing polyphenols was constructed. This example uses epigallocatechin gallate (EGCG) as an illustration of the detection process.

[0096] like Figure 7 As shown, we further determined the type of defects and changes in surface composition during the enzymatic reaction and sensing process using XPS. The deconvolution V 2p XPS spectrum of α-Ag3VO4 was at 516.67 (V 4+ 2 p1 / 2 ) and 524.09 eV (V 5+ 2 p3 / 2 It has two characteristic peaks. Due to the need for charge balance, V 4+ The presence of [something] leads to the formation of oxygen vacancies. From [something] Figure 8 In the O 1s XPS spectrum, the peak at 531.19 eV is a typical marker of reported hypoxia (O 1s XPS). V (i.e., oxygen vacancies) can also be used to verify this conclusion.

[0097] like Figure 9 As shown, when EGCG is added to the α-Ag3VO4+ TMB system, the O in solid α-Ag3VO4... V The signal is still preserved, with a g value of 2.0052 (oxygen vacancy).

[0098] like Figure 10 and Figure 11 As shown, within 1 minute, the absorbance of the α-Ag3VO4+ TMB blank solution at 652 nm gradually increased with the increase of EGCG concentration from 0.1 μM to 1 M, and the increase in absorbance showed a linear relationship with the change in EGCG concentration, indicating that the sensor has high sensitivity to EGCG. This makes it possible to quantitatively detect EGCG using this sensor. From this linear relationship, it can be seen that under the test conditions, the preliminary detection limit of α-Ag3VO4+ TMB for EGCG is 0.1586 μM, and the detection range is 1.0 μM-9.0 μM.

[0099] The above example provides a colorimetric sensor based on an "off-on model," which can co-precipitate flower-like α-Ag3VO4 nanozyme particles in an ammoniacal silver solution precursor. Utilizing the property of polyphenols as free radical scavengers to inhibit enzymatic reactions, a sensor platform for the typical polyphenol EGCG was established. To date, this is the only nanozyme-based chemical sensor that can be used to detect the signal of reduced polyphenols using an "off-on model."

[0100] The beneficial effects of this invention are:

[0101] This method for preparing flower-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor prepares flower-shaped Ag3VO4 nanozymes through co-precipitation. It achieves colorimetric quantitative detection of natural or artificially synthesized polyphenolic compounds with specific structures by using a signal "off-on" mode instead of the traditional "on-off" mode, thus solving problems such as high background noise, insufficient signal resolution, and difficulty in visual observation.

[0102] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing flower-like silver vanadate nanozymes based on silver ammonia solution as a precursor, characterized in that, Includes the following steps: S1. Preparation of silver ammonia solution: Based on silver nitrate solution and sodium hydroxide solution, the prepared silver ammonia solution is used as a precursor; S2. Preparation of α-Ag3VO4 nanozyme without the addition of sodium nitrate; S3. Preparation of α-Ag3VO4 nanozyme with added sodium nitrate; S4. Detect the presence or absence of sodium nitrate in the two types of α-Ag3VO4 nanozymes; S5. Detect the oxidase activity of α-Ag3VO4 with added sodium nitrate; S6. Using α-Ag3VO4 with added sodium nitrate, gallocatechin gallate (EGCG) was quantitatively detected colorimetrically in a signal-enhanced "off-on" mode.

2. The method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 1, characterized in that, In step S1, the preparation of the silver ammonia solution includes the following specific process: Weigh 4.25g of silver nitrate solid and add it to a 100ml beaker. Then add 50ml of deionized water to the beaker to completely dissolve the silver nitrate and prepare a 0.5mol / L silver nitrate solution, which is called solution A. Weigh 0.2g of sodium hydroxide solid and add it to 100ml of deionized water in a 250ml beaker. Stir until completely dissolved to obtain a 0.05mol / L sodium hydroxide solution, which is used as solution B. Slowly add solution B to solution A while stirring continuously, and a brown precipitate will form; Measure 1.25 ml of concentrated ammonia solution and add it to a 50 ml beaker. Then add 30 ml of deionized water to the beaker to prepare dilute ammonia solution. Slowly add dilute ammonia solution dropwise into the brown precipitate while stirring continuously until the precipitate just disappears. The resulting solution is a silver ammonia solution.

3. The method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 1, characterized in that, In step S2, the preparation of α-Ag3VO4 nanozyme without the addition of sodium nitrate includes the following specific process: Take a 100ml beaker, add 2.92g of ammonium metavanadate solid to the beaker, then measure 50ml of deionized water and add it to the beaker. Stir at room temperature to dissolve it completely, and you will get a 0.5mol / L NH4VO3 solution. Silver ammonia solution and NH4VO3 solution were added dropwise at a mass ratio of 1:1, stirred thoroughly, and then placed in a reaction vessel and reacted at 80°C for 24 hours. After the reaction is complete, cool to room temperature, pour the obtained solid into a centrifuge tube and centrifuge at high speed. The centrifugation rate is set to 8000 r per minute and the centrifugation time is set to 5 min. The solid was washed, and after washing, the product was placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain α-Ag3VO4 nanozyme without sodium nitrate.

4. The method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 3, characterized in that, During washing, the solid is first centrifuged three times with deionized water, and then centrifuged three times with anhydrous ethanol to complete the washing process.

5. The method for preparing flower-like silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 1, characterized in that, In step S3, the preparation of α-Ag3VO4 nanozyme with added sodium nitrate includes the following specific process: Weigh out two portions of 2.125g NaNO3, add one portion to the silver ammonia solution used as a precursor, and stir thoroughly to obtain a silver ammonia-sodium nitrate solution; Take a 100ml beaker, add 2.92g of ammonium metavanadate solid to the beaker, then measure 50ml of deionized water and add it to the beaker. Stir at room temperature to dissolve it completely, and you will get a 0.5mol / L NH4VO3 solution. Add another portion of NaNO3 to the NH4VO3 solution and stir until homogeneous to obtain an NH4VO3-NaNO3 solution; The prepared silver ammonia-sodium nitrate solution and NH4VO3-NaNO3 solution were added dropwise at a mass ratio of 1:

1. After thorough stirring, the mixture was placed in a reaction vessel and reacted at 80°C for 24 hours. After the reaction is complete, cool to room temperature, pour the obtained solid into a centrifuge tube and centrifuge at high speed. The centrifugation rate is set to 8000 r per minute and the centrifugation time is set to 5 min. The solid was washed, and after washing, the product was placed in a vacuum drying oven and dried at 70°C for 3 hours to obtain α-Ag3VO4 nanozyme with added sodium nitrate.

6. The method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 1, characterized in that, In step S4, based on the field emission scanning electron microscope (SEM) measurement results, flower cluster-shaped α-Ag3VO4 nanozymes are selected; Field emission scanning electron microscopy (SEM) measurements showed that the synthesized α-Ag3VO4 with added NaNO3 had a flower-like morphology with distinct shapes and no other impurities or particles. In contrast, the α-Ag3VO4 without added NaNO3 also showed a flower-like morphology, but the particles were not as distinct.

7. The method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 1, characterized in that, In step S5, the detection process includes the following specific steps: With a total reaction volume of 3 mL, 0.04 mg / mL of α-Ag3VO4 solution was added to NaAc-HAc buffer solution with a pH of 4, shaken well, and then 0.15 mmol / L of TMB solution was added. The mixture was stirred evenly and reacted at room temperature for 31 min.

8. The method for preparing flower cluster-shaped silver vanadate nanozymes based on silver ammonia solution as a precursor according to claim 7, characterized in that, The preparation processes for the TMB solution and the α-Ag3VO4 solution include the following: TMB solution: At room temperature, add 7.2 mg of TMB powder to 2 mL of anhydrous ethanol. After complete dissolution, store the solution in a refrigerator at 4°C away from light for later use. For the α-Ag3VO4 solution, measure 2 mL of H2O, disperse 6 mg of silver vanadate powder in it, and sonicate at room temperature for 30 min until evenly dispersed. In subsequent experiments, shake well before use.

Images