Gold nanostar with core-shell structure as well as preparation method and application of gold nanostar

Abstract

The invention belongs to the field of synthesis of nano materials, and particularly relates to a core-shell structure gold nano star and a preparation method and application thereof, and the core-shell structure gold nano star comprises a first gold nano star containing a metal sulfide shell layer and a second gold nano star containing a metal oxide shell layer. The preparation method comprises the following steps: firstly preparing a gold nano star core solution, and then respectively adding different precursors to prepare two core-shell structure gold nano stars. The method has the advantages of simple synthesis conditions and non-toxic reagents. The core-shell structure gold nanostars are used for preparing a detection solution based on a buffer solution, a color developing agent and an oxidizing agent, the detection solution reacts with antioxidants, a data matrix is constructed by measuring absorbance changes and is analyzed, single, binary and ternary combinations of various antioxidants such as ascorbic acid and glutathione can be accurately distinguished, and the detection accuracy is improved. The application prospect in the fields of biomolecules and food detection is good.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of functional nanomaterials, and specifically relates to a gold nanosphere with a core-shell structure, its preparation method and application. Background Art

[0002] At present, the synthesis conditions of common nanozymes are harsh, the reaction takes a long time and some toxic reagents are often used. The synthesis conditions of the gold nanosphere with a core-shell structure are simple, the reaction is rapid, the reagents required for the reaction are common and non-toxic, and it has good peroxidase activity. By constructing a colorimetric sensing array, different antioxidants can be accurately identified. The gold nanosphere itself has certain peroxidase activity, but it is easily etched or aggregated during the reaction process. The construction of the core-shell structure makes the material more stable.

[0003] Antioxidants are one of the very important nutritional components of food, and are divided into natural antioxidants and artificially added antioxidants. Natural antioxidants such as ascorbic acid, polyphenols and tocopherols are mostly a chemical means evolved by plants themselves to resist reactive oxygen species, the by-products of photosynthesis. Artificially added antioxidants are mostly some synthetic chemicals that can prevent food spoilage caused by the oxidation of unsaturated fatty acids. According to research, consuming foods rich in antioxidants can reduce the oxidative stress response caused by reactive oxygen species and reactive nitrogen species, thereby greatly reducing the risk of diseases caused by oxidative stress, such as some neurological diseases, cancers, and some heart diseases. The qualitative and quantitative detection of antioxidants has now become one of the important indicators for evaluating food quality.

[0004] So far, many methods for detecting antioxidants have been reported and applied, such as some traditional methods like high performance liquid chromatography, Raman spectroscopy, infrared spectroscopy, electrophoresis, etc. Although these methods can all detect antioxidants, they all have some obvious defects, such as: expensive equipment, professional operation, high cost, cumbersome sample processing, long time consumption, etc. In order to overcome these disadvantages, more and more simple and convenient biosensing methods have received attention. At the same time, some new types of nanomaterials are used to improve the sensitivity and specificity of antioxidant detection. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the present invention innovatively develops a gold nanosphere with a core-shell structure, its preparation method and application. Through the core-shell structure design and simple synthesis method, the present invention solves the problems of poor stability and complex detection method of traditional nanomaterials, and shows significant advantages of high efficiency, accuracy and low cost in antioxidant detection.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] In the first aspect, the present invention provides a gold nanosphere with a core-shell structure, including:

[0008] The first gold nanosphere, comprising a star-shaped gold nanosphere core and a metal sulfide shell layer coated on the surface of the gold nanosphere core;

[0009] The second gold nanosphere, comprising a star-shaped gold nanosphere core and a metal oxide shell layer coated on the surface of the gold nanosphere core.

[0010] As a further optimized solution of the present invention, the metal sulfide includes iron sulfide, and the metal oxide includes copper oxide.

[0011] As a further optimized solution of the present invention, the particle size of the gold nanosphere core is 70 - 90 nm, the thickness of the metal sulfide shell layer is 20 - 25 nm, and the thickness of the metal oxide shell layer is 5 - 10 nm.

[0012] In a second aspect, the present invention provides a method for the gold nanosphere with the core-shell structure as described above, comprising the following steps:

[0013] Prepare a gold nanosphere core solution;

[0014] Place the gold nanosphere core solution in a reaction vessel, adjust the pH to 12 - 14, add a sulfur source and a metal sulfide precursor to the solution for reaction, after the reaction is completed, centrifuge and wash, and freeze-dry to obtain the first gold nanosphere with a core-shell structure;

[0015] Place the gold nanosphere core solution in a reaction vessel, adjust the pH to 12 - 14, add a reducing agent and a metal oxide precursor to the solution for reaction, after the reaction is completed, centrifuge and wash, and freeze-dry to obtain the second gold nanosphere with a core-shell structure.

[0016] The reaction mechanism for preparing the first gold nanosphere with a core-shell structure is as follows: under strong alkaline conditions (pH = 12 - 14), thiourea (the sulfur source) undergoes hydrolysis and decomposition reactions, gradually releasing sulfide ions (S 2- ), and ferrous chloride (the metal sulfide precursor) in the solution provides Fe 2+ . Since the surface of the gold nanosphere core is negatively charged due to the modification of sodium citrate or PVP, it adsorbs positively charged Fe 2+ through electrostatic interaction, and then reacts with S 2- , and FeS nanoparticles are deposited layer by layer on the surface of the gold core, forming a uniform iron sulfide shell layer. Thiourea acts as both a sulfur source and a weak reducing agent in this process, preventing Fe 2+ from being oxidized to Fe 3+ , ensuring the purity of the shell layer.

[0017] The reaction mechanism for preparing the second gold nanostar with a core-shell structure is as follows: The formation of CuO mainly depends on the combined action of a strong alkaline environment (pH = 12 - 14) and the reduction of ascorbic acid, which promotes the generation of CuO and the control of its morphology. This process does not require high temperature, and the efficient deposition of CuO can be achieved through chemical regulation, ultimately forming the second gold nanostar with a core-shell structure.

[0018] As a further optimization scheme of the present invention, the sulfur source includes thiourea, and the metal sulfide precursor includes ferrous chloride; the mass ratio of the gold nanostar core to ferrous chloride is (3.5 - 4.5):1.

[0019] As a further optimization scheme of the present invention, the reducing agent includes ascorbic acid, and the metal oxide precursor includes copper chloride; the mass ratio of the gold nanostar core to copper chloride is (3 - 4):1.

[0020] As a further optimization scheme of the present invention, the preparation method of the gold nanostar core solution includes:

[0021] (1) At 90 - 110 °C, mix and react the chloroauric acid solution with the sodium citrate solution to generate spherical gold nanoparticles;

[0022] (2) Mix the spherical gold nanoparticles with chloroauric acid, silver nitrate, and hydrochloric acid solution, add ascorbic acid under stirring conditions for a reduction reaction, and then add PVP to stabilize the morphology;

[0023] (3) Centrifuge the reaction product to remove unreacted substances, and obtain the gold nanostar core solution after repeated washing.

[0024] The reaction mechanism for preparing the gold nanostar core solution is as follows: The first step (synthesis of spherical gold nanoparticles): At 90 - 110 °C, sodium citrate acts as a reducing agent and a stabilizer to reduce chloroauric acid (HAuCl4) to gold atoms (Au 0 ), and the gold atoms aggregate to form spherical gold nanoparticles. Sodium citrate adsorbs on the particle surface to prevent aggregation. The second step (synthesis of gold nanostar cores): Add silver nitrate (AgNO3), hydrochloric acid (HCl), and ascorbic acid to the spherical gold nanoparticle solution. Ag + acts as a seed guiding agent to promote the anisotropic growth of gold nanoparticles under acidic conditions; ascorbic acid further reduces chloroauric acid to provide gold atoms for directional deposition on the surface of the spherical particles, forming star-shaped tips; PVP (polyvinylpyrrolidone) adsorbs on the surface of the gold nanostars to stabilize their star-shaped structure and prevent aggregation. Finally, a pure gold nanostar core solution is obtained through centrifugation and washing.

[0025] As a further optimization scheme of the present invention, in step (1), the molar ratio of chloroauric acid to sodium citrate is 1:(12 - 14); in step (2), the mass ratio of spherical gold nanoparticles, silver nitrate and chloroauric acid is 1:(9 - 11):(45 - 55).

[0026] In the third aspect, the present invention provides an application of the gold nanorods with the core - shell structure in detecting antioxidants, and the antioxidants include any one, two or three combinations of ascorbic acid, glutathione, cysteine, gallic acid, tannic acid, uric acid, sodium citrate, caffeic acid.

[0027] As a further optimization scheme of the present invention, the antioxidant detection method includes the following steps:

[0028] Based on a buffer solution, a chromogenic agent and an oxidant, respectively prepare a first detection solution containing the first gold nanorods and a second detection solution containing the second gold nanorods;

[0029] React the first detection solution and the second detection solution with the antioxidant to be measured respectively, and measure the absorbance change of the reaction system at preset time nodes to obtain absorbance data at multiple time nodes;

[0030] Construct a multi - dimensional data matrix based on the absorbance data, and process the data matrix by a multivariate statistical analysis method to distinguish the types of antioxidants;

[0031] Among them, the mass ratio of the first gold nanorods to the second gold nanorods is 1:(1 - 2).

[0032] Compared with the prior art, the beneficial effects obtained by the present invention are as follows:

[0033] (1) Most of the current synthesis of nanozymes requires high temperature and high pressure and long - time reactions, and the synthesis process is time - consuming and energy - consuming. The present invention uses common non - toxic reagents, avoids using toxic solvents, the reaction is carried out at normal temperature and pressure, without high temperature and high pressure, with short time consumption and low energy consumption, significantly reducing the synthesis cost and operation risk.

[0034] (2) Gold nanorods themselves have certain peroxidase activity, but are easily etched or aggregated during the reaction, losing enzyme activity and affecting the color development of the chromogenic agent at the same time. The present invention coats a metal sulfide (such as FeS) or a metal oxide (such as CuO) shell layer on the surface of the gold nanorod core to form a core - shell structure, effectively preventing the gold nanorods from being etched or aggregated during the reaction, maintaining the stability of their peroxidase activity, ensuring the accuracy of the color development reaction, and avoiding detection errors caused by material inactivation.

[0035] (3) Currently, the common detection methods for antioxidants have many disadvantages, such as expensive equipment, long time consumption, and the need for professional operation. Based on two kinds of core-shell structured gold nanorods, the present invention constructs a colorimetric array, constructs a multi-dimensional data matrix through absorbance changes, and uses multivariate statistical analysis methods (such as LDA, HCA, etc.) to accurately distinguish 8 kinds of antioxidants (including single, binary, and ternary combinations), covering common antioxidants such as ascorbic acid (AA), glutathione (GSH), etc. Compared with traditional detection methods (such as high performance liquid chromatography, Raman spectroscopy), it has the advantages of simple operation, low cost, and fast speed, and is applicable to fields such as biomolecule detection and food quality evaluation. Brief Description of the Drawings

[0036] Figure 1 It is the morphology diagram of the spherical gold nanoparticles prepared in Example 1 of the present invention under a scanning electron microscope.

[0037] Figure 2 It is the morphology diagram of the gold nanorod core prepared in Example 1 of the present invention under a scanning electron microscope.

[0038] Figure 3 It is the morphology diagram of AuNSs@FeS prepared in Example 1 of the present invention under a scanning electron microscope.

[0039] Figure 4 It is the morphology diagram of AuNSs@CuO prepared in Example 1 of the present invention under a scanning electron microscope.

[0040] Figure 5 It is the morphology diagram of AuNSs@CuS prepared in Comparative Example 1 of the present invention under a scanning electron microscope.

[0041] Figure 6 It is the morphology diagram of AuNSs@CuSe prepared in Comparative Example 2 of the present invention under a scanning electron microscope.

[0042] Figure 7 It is the XPS energy spectrum characterization diagram of AuNSs@FeS prepared in Example 1 of the present invention.

[0043] Figure 8 It is the XPS energy spectrum characterization diagram of AuNSs@CuO prepared in Example 1 of the present invention.

[0044] Figure 9 It is the influence of pH value on the detection performance of materials in Experimental Example 1 of the present invention.

[0045] Figure 10 It is the stability kinetic study of AuNSs@FeS with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0046] Figure 11This is the study on the stable kinetics (double reciprocal curve) of AuNSs@FeS with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0047] Figure 12 This is the study on the stable kinetics of AuNSs@CuO with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0048] Figure 13 This is the study on the stable kinetics (double reciprocal curve) of AuNSs@CuO with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0049] Figure 14 This is the study on the stable kinetics of AuNSs@CuS with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0050] Figure 15 This is the study on the stable kinetics (double reciprocal curve) of AuNSs@CuS with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0051] Figure 16 This is the study on the stable kinetics of AuNSs@CuSe with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0052] Figure 17 This is the study on the stable kinetics (double reciprocal curve) of AuNSs@CuSe with hydrogen peroxide as the substrate in Experimental Example 2 of the present invention.

[0053] Figure 18 This is the linear discriminant analysis (LDA) of the colorimetric array for detecting five antioxidants by selecting three time points of 20 min, 30 min, and 40 min to construct a two-material × three-time-point × five-antioxidant × eight-replicate colorimetric array in Example 4 of the present invention.

[0054] Figure 19 This is the linear discriminant analysis (LDA) of the colorimetric array for detecting five antioxidants by selecting three time points of 30 min, 60 min, and 90 min to construct a two-material × three-time-point × five-antioxidant × eight-replicate colorimetric array in Example 4 of the present invention.

[0055] Figure 20 This is the linear discriminant analysis (LDA) of the colorimetric array for detecting five antioxidants by selecting two time points of 30 min and 60 min to construct a two-material × three-time-point × eight-antioxidant × eight-replicate colorimetric array in Example 4 of the present invention.

[0056] Figure 21 This is the fingerprint of the colorimetric array for detecting eight antioxidants in Example 4 of the present invention.

[0057] Figure 22This is the heat map of the colorimetric array detecting eight antioxidants in Example 4 of the present invention.

[0058] Figure 23 This is the hierarchical cluster analysis (HCA) of the colorimetric array detecting eight antioxidants in Example 4 of the present invention.

[0059] Figure 24 This is the decision tree of the colorimetric array detecting eight antioxidants in Example 4 of the present invention.

[0060] Figure 25 This is the training set matrix and test set matrix of the colorimetric array detecting eight antioxidants in Example 4 of the present invention.

[0061] Figure 26 This is the linear discriminant analysis (LDA) of the colorimetric array detecting nine groups of binary mixed antioxidants in Example 4 of the present invention.

[0062] Figure 27 This is the hierarchical cluster analysis (HCA) of the colorimetric array detecting nine groups of binary mixed antioxidants in Example 4 of the present invention.

[0063] Figure 28 This is the linear discriminant analysis (LDA) of the colorimetric array detecting six groups of ternary mixed antioxidants in Example 4 of the present invention.

[0064] Figure 29 This is the hierarchical cluster analysis (HCA) of the colorimetric array detecting six groups of ternary mixed antioxidants in Example 4 of the present invention. Detailed implementation manners

[0065] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the preferred implementation manners of the present invention will be described below in conjunction with specific embodiments, but it should not be construed as a limitation of the present invention, and only for example.

[0066] Example 1

[0067] This example provides a preparation method of gold nanorods with a core-shell structure, including the following steps:

[0068] Step 1. Preparation of the gold nanorod core solution:

[0069] A) Synthesis of spherical gold nanoparticles: Take a clean and dried 250 ml round-bottom flask and place it on a thermostatic heating magnetic stirrer, put a clean magnetic stir bar, set the temperature to 100 °C, and the stirring speed to 500 rpm. Add 150 ml of a 2 mM sodium citrate aqueous solution and 1 ml of a 25 mM chloroauric acid aqueous solution to the round-bottom flask. Heat and react until the solution changes from light gold to wine red to obtain gold nanoparticles with a size of 10 nm.

[0070] B) Synthesis of gold nanosphere cores: Take a washed and dried 500 ml round-bottom flask and place it on a thermostatic heating (maintaining 25 °C) magnetic stirrer. Put a clean magnetic stir bar and set the stirring speed to 1200 rpm. Add 300 ml of ultrapure water, 600 μl of 1 M HCl, and 3 ml of 50 mM chloroauric acid to the round-bottom flask. After stirring evenly, add 18 ml of the above spherical gold nanoparticles and 1.2 ml of 50 mM silver nitrate solution. The mass ratio of spherical gold nanoparticles, silver nitrate, and chloroauric acid is 1:10:50. Stir for five minutes until homogeneous. Finally, quickly add 3 ml of 0.1 M ascorbic acid at once. The solution quickly turns dark blue-gray. Weigh 1 g of PVP (polyvinylpyrrolidone) and add it. Stir for 5 min. Pour the product into 50 ml centrifuge tubes in batches, place them in a centrifuge, set the rotation speed to 10000 rpm, and the time to 5 min. After centrifugation, discard the supernatant. Re-add ultrapure water to the centrifuge tubes, ultrasonicate to redissolve, and then centrifuge again. Repeat three times to obtain a washed gold nanosphere core solution.

[0071] Step 2. Preparation of gold nanospheres with core-shell structure:

[0072] C) Synthesis of AuNSs@FeS: Take a washed and dried 500 ml round-bottom flask and place it on a thermostatic heating (maintaining 25 °C) magnetic stirrer. Put a clean magnetic stir bar. Re-add the above washed gold nanosphere core solution to the flask. Add 0.1 M sodium hydroxide to adjust the pH to 14. Add 6 ml of 0.1 M thiourea and stir for 10 min. Add 3 ml of 0.1 M ferrous chloride and react for 0.5 h. The mass ratio of gold nanosphere cores to ferrous chloride is 4:1. Pour the product into centrifuge tubes in batches, place them in a centrifuge, set the rotation speed to 10000 rpm, and the time to 5 min. After centrifugation, discard the supernatant. Re-add ultrapure water to the centrifuge tubes, ultrasonicate to redissolve, and then centrifuge again. Repeat three times to obtain a washed AuNSs@FeS solution. Store it by freeze-drying to obtain the first gold nanospheres (AuNSs@FeS).

[0073] D) Synthesis of AuNSs@CuO: Place a cleaned and dried 500 ml round-bottom flask on a thermostatic heating (maintaining 25 °C) magnetic stirrer and put a clean magnetic stir bar. Re-add the above-mentioned cleaned gold nanosphere core solution into the flask, add 0.1 M sodium hydroxide to adjust the pH to 14, add 3 ml of 0.1 M copper chloride solution, and then quickly add 3 ml of 1 M ascorbic acid (ensuring an excess) at once. React for 0.5 h. The mass ratio of the gold nanosphere core to copper chloride is 3.5:1. Pour the product into centrifuge tubes in batches, place it in a centrifuge, set the rotation speed to 10,000 rpm and the time to 5 min. After centrifugation, discard the supernatant. Re-add ultrapure water to the centrifuge tube, ultrasonicate to redissolve and then centrifuge again. Repeat three times to obtain a cleaned AuNSs@CuO solution, freeze-dry and store it to obtain the second gold nanosphere (AuNSs@CuO).

[0074] Figure 1 It indicates that spherical gold nanoparticles with uniform size (diameter 10 - 12 nm) were successfully synthesized; Figure 2 It indicates that gold nanosphere cores with standard morphology and uniform size (diameter 70 - 90 nm) were successfully synthesized. Figure 3 and Figure 4 It indicates that AuNSs@FeS and AuNSs@CuO with standard morphology were successfully synthesized. Figure 7 This is the XPS full spectrum of AuNSs@FeS, and all the elements contained in the material can be corresponded to the spectrum Figure 1 one by one; Figure 8 This is the XPS full spectrum of AuNSs@CuO, and all the elements contained in the material can be corresponded to the spectrum Figure 1 one by one.

[0075] Example 2:

[0076] The difference between this example and Example 1 is as follows: In A), set the temperature to 90 °C, the stirring speed to 400 rpm, and the molar ratio of chloroauric acid to sodium citrate to 1:13; in B), the mass ratio of spherical gold nanoparticles, silver nitrate and chloroauric acid is 1:9:45; in C), adjust the pH to 12, the mass ratio of gold nanosphere core to ferrous chloride is 3.5:1, and the reaction time is 1 h; in D), adjust the pH to 12, the mass ratio of gold nanosphere core to copper chloride is 3:1, and the reaction time is 1 h. Finally, core-shell structured AuNSs@FeS and AuNSs@CuO are obtained.

[0077] Example 3:

[0078] The differences between this embodiment and Embodiment 1 are as follows: In A), the temperature is set at 110 °C, the stirring speed is 600 rpm, and the molar ratio of chloroauric acid to sodium citrate is 1:14; in B), the mass ratio of spherical gold nanoparticles, silver nitrate and chloroauric acid is 1:11:55; in C), the pH is adjusted to 13, the mass ratio of gold nanosphere core to ferrous chloride is 4:1, and the reaction time is 2 h; in D), the pH is adjusted to 13, the mass ratio of gold nanosphere core to copper chloride is 4:1, and the reaction time is 2 h. Finally, the core-shell structured AuNSs@FeS and AuNSs@CuO are obtained.

[0079] Example 4: Construction of a colorimetric sensing array and qualitative detection of eight antioxidants

[0080] Select the first gold nanospheres (AuNSs@CuO) and the second gold nanospheres (AuNSs@FeS) prepared in Example 1 to construct a colorimetric array. Dissolve 2 mg of each gold nanosphere material in 2 ml of ultrapure water to prepare two gold nanosphere material solutions with a concentration of 1 mg / ml. Take 5 ml of acetic acid-sodium acetate buffer (for AuNSs@FeS, take the buffer solution with pH 2; for AuNSs@CuO, take the buffer solution with pH 4), 500 μL of hydrogen peroxide with a concentration of 10 mM, 500 μL of TMB (3,3',5,5'-tetramethylbenzidine) with a concentration of 10 mM and 500 μL of the two prepared gold nanosphere material solutions and mix them evenly to obtain the first detection solution containing the first gold nanospheres and the second detection solution containing the second gold nanospheres, and set aside for use.

[0081] Prepare 1 ml of 1 mM each of ascorbic acid (AA), glutathione (GSH), cysteine (Cys), gallic acid (TA), tannic acid (GA), uric acid (UA), sodium citrate (SC), and caffeic acid (CA) and pre-add them to a 96-well plate.

[0082] Heat the first detection solution and the second detection solution in a water bath at 60 °C for 5 min, then use a multi-channel pipette to take 100 μl from each well and add it to the 96-well plate that has already been added with antioxidants, and quickly put it into an enzyme-labeled instrument to monitor the change in absorbance (each antioxidant is repeated eight times for each material). Try to form a colorimetric array at different time points. Finally, according to the results of the colorimetric array, take the data at 10 min and 15 min to construct a data matrix of two materials × two time points × eight antioxidants × eight repetitions, and perform linear discriminant analysis (LDA), cluster analysis (HCA) and decision tree analysis on the data to distinguish and detect the single components of the eight antioxidants.

[0083] Similarly, binary mixed antioxidants with a total concentration of 1 mM were prepared (AA:SC = 1:4, AA:SC = 1:1, AA:SC = 4:1, AA:GSH = 1:4, AA:GSH = 1:1, AA:GSH = 4:1, AA:CA = 1:4, AA:CA = 1:1, AA:CA = 4:1), and linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA) were performed using the constructed colorimetric array to distinguish and detect the two combined components of the eight antioxidants.

[0084] Similarly, ternary mixed antioxidants with a total concentration of 1 mM were prepared (AA:GSH:SC = 2:1:1, AA:GSH:SC = 1:2:1, AA:GSH:SC = 1:1:2, UA:Cys:CA = 2:1:1, UA:Cys:CA = 1:2:1, UA:Cys:CA = 1:1:2), and linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA) were performed using the constructed colorimetric array to distinguish and detect the three combined components of the eight antioxidants.

[0085] Figure 18 and Figure 19 It shows that when incorrect sensing elements are selected, two or more antioxidants cannot be fully distinguished; Figure 20 It shows that when the correct and appropriate sensing elements are selected, all eight antioxidants are fully distinguished by the colorimetric array; Figure 21 It shows that when the eight antioxidants are fully distinguished, there are also certain differences in the fingerprint spectra during recognition; Figure 22 It shows that when the eight antioxidants are fully distinguished, there are also certain differences in the heat maps during recognition; Figure 23 It shows that when the eight antioxidants are fully distinguished, the eight antioxidants can also be exactly divided into eight categories using hierarchical cluster analysis; Figure 24 It shows that by performing a decision tree analysis on the colorimetric sensing array, it can be seen that four sensing elements are well utilized to well distinguish the eight antioxidants; Figure 25 It shows that from the confusion matrix of the decision tree analysis, it can be seen that whether it is the training set or the test set, the accuracy of the colorimetric sensing array in recognizing the eight antioxidants can reach 100%; Figure 26 It shows that by selecting several antioxidants with relatively high and common contents in food, pairwise mixing them in different proportions to form binary mixtures with the same concentration, and using the colorimetric sensing array for recognition, they can be fully distinguished; Figure 27 Figure 28 It shows that by selecting several antioxidants with relatively high and common contents in food, mixing them in different proportions to form ternary mixtures with the same concentration, and using the colorimetric sensing array for recognition, they can be fully distinguished; Figure 29 ​It is shown that in the cluster analysis identified by the ternary mixed antioxidant, it is correctly classified into eight categories.

[0086] Comparative Example 1:

[0087] In this comparative example, the gold nanosphere core solution prepared in Example 1 was used. Synthesis of AuNSs@CuS: Take a 500 ml round-bottom flask washed and dried and place it on a thermostatic heating magnetic stirrer, and put a clean magnetic stir bar. Re-add the above-mentioned washed gold nanosphere core solution into the flask, adjust the pH to 14, add 6 ml of thiourea with a concentration of 0.1 M, stir for 10 min, add 3 ml of copper chloride with a concentration of 0.1 M, and react for 0.5 - 2 h. Pour the product into centrifuge tubes in batches, place them in a centrifuge, set the rotation speed to 10,000 rpm and the time to 5 min. After centrifugation, discard the supernatant. Re-add ultrapure water to the centrifuge tubes, ultrasonically redissolve, and then centrifuge again. Repeat three times to obtain a washed AuNSs@CuS solution, which is stored by freeze-drying. It can be seen from Figure 5 that AuNSs@CuS with standard morphology was synthesized.

[0088] Comparative Example 2:

[0089] In this comparative example, the gold nanosphere core solution prepared in Example 1 was used. Synthesis of AuNSs@CuSe: Take a 500 ml round-bottom flask washed and dried and place it on a thermostatic heating magnetic stirrer, and put a clean magnetic stir bar. Re-add the above-mentioned washed gold nanosphere core solution into the flask, adjust the pH to 14, add 3 ml of sodium selenite solution with a concentration of 0.1 M, and then quickly add 3 ml of ascorbic acid with a concentration of 1 M (ensure an excess) at one time, react for 0.5 - 2 h, then add 3 ml of copper chloride solution with a concentration of 0.1 M, and then quickly add 3 ml of ascorbic acid with a concentration of 1 M (ensure an excess) at one time, and react for 0.5 - 2 h. Pour the product into centrifuge tubes in batches, place them in a centrifuge, set the rotation speed to 10,000 rpm and the time to 5 min. After centrifugation, discard the supernatant. Re-add ultrapure water to the centrifuge tubes, ultrasonically redissolve, and then centrifuge again. Repeat three times to obtain a washed AuNSs@CuSe solution, which is stored by freeze-drying. It can be seen from Figure 6 that AuNSs@CuSe with standard morphology was synthesized.

[0090] Experimental Example 1: Effect of pH on the enzymatic activity of the material

[0091] Dissolve 5 mg of the material in 5 ml of ultrapure water to prepare a solution with a concentration of 1 mg / ml. Take 100 μl of acetic acid-sodium acetate buffer with different pH values (pH ranging from 2 to 8), 10 μL of hydrogen peroxide with a concentration of 10 mM, 10 μL of TMB with a concentration of 10 mM, and 10 μl of the prepared solution, mix them evenly, place them in a water bath at 37 °C for 5 min, and use an ultraviolet-visible spectrophotometer to detect the ultraviolet absorption peak at a wavelength of 652 nm respectively. As can be seen from Figure 9 , when pH = 2, the reaction of AuNSs@FeS is the best; when pH = 4, the reaction of AuNSs@CuO is the best; the enzyme activities of AuNSs@CuS and AuNSs@CuSe are poor.

[0092] Experimental Example 2: Determination of Michaelis constant

[0093] Dissolve 2 mg of the material in 2 mL of ultrapure water to prepare a 1 mg / mL solution, and prepare hydrogen peroxide solutions with different concentrations (200 μM, 4,00 μM, 600 μM, 800 μM, 1,000 μM, 1,200 μM, 1,400 μM, 1,600 μM, 1,800 μM, 2,000 μM). Take 100 μL of acetic acid-sodium acetate buffer (for AuNSs@FeS, take the buffer solution with pH = 2; for AuNSs@CuO, take the buffer solution with pH = 4), 10 μL of hydrogen peroxide with different concentrations, 10 μL of TMB with a concentration of 10 mM, and 10 μL of the prepared solution, mix them evenly, heat them in a water bath at 60 °C for 5 min, use an ultraviolet-visible spectrophotometer to detect the ultraviolet absorption peak at a wavelength of 652 nm respectively, calculate the reaction rate using the peak value, make a double-reciprocal curve of the reaction rate versus the hydrogen peroxide concentration, and calculate the Michaelis constant. The results show that AuNSs@CuO and AuNSs@FeS have a smaller Michaelis constant and a higher substrate affinity.

[0094] Figure 10 It shows that: the curve of the kinetic study of AuNSs@FeS with hydrogen peroxide as the substrate, where Km = 0.79 and Vmax = 1.09×10^-7; Figure 11 It shows that: the double-reciprocal curve of the kinetic study of AuNSs@FeS with hydrogen peroxide as the substrate, R 2 = 0.97, and the fitting degree is better; Figure 12 It shows that: the curve of the kinetic study of AuNSs@CuO with hydrogen peroxide as the substrate, where Km = 0.40 and Vmax = 3.31×10^-8; Figure 13 It shows that: the double-reciprocal curve of the kinetic study of AuNSs@CuO with hydrogen peroxide as the substrate, R 2 = 0.98, and the fitting degree is better; Figure 14It shows that for the curve of the kinetic study of AuNSs@CuS with hydrogen peroxide as the substrate, the enzyme activity is extremely poor and cannot be fitted; Figure 15 It shows that for the double-reciprocal curve of the kinetic study of AuNSs@CuS with hydrogen peroxide as the substrate, the enzyme activity is extremely poor and the fitting degree is poor; Figure 16 It shows that for the curve of the kinetic study of AuNSs@CuSe with hydrogen peroxide as the substrate, the enzyme activity is extremely poor and cannot be fitted; Figure 17 It shows that for the double-reciprocal curve of the kinetic study of AuNSs@CuSe with hydrogen peroxide as the substrate, the enzyme activity is extremely poor and the fitting degree is poor.

[0095] The above are only the preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations on the present invention. The protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art, without departing from the spirit and scope of the present invention, several improvements and refinements can also be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Gold nanostars with a core-shell structure, characterized in that: include: A first gold nanostar comprises a star-shaped gold nanostar core and a metal sulfide shell layer coated on the surface of the gold nanostar core; The second gold nanostar includes a star-shaped gold nanostar core and a metal oxide shell layer covering the surface of the gold nanostar core.

2. The core-shell gold nanostar according to claim 1, characterized in that The metal sulfide includes ferrous sulfide, and the metal oxide includes copper oxide.

3. The core-shell gold nanostar according to claim 1, characterized in that The particle size of the gold nanostar core is 70-90 nm, the thickness of the metal sulfide shell is 20-25 nm, and the thickness of the metal oxide shell is 5-10 nm.

4. A method for preparing the core-shell gold nanostar according to claim 1, characterized in that: The steps include: Prepare gold nanostar core solution; The gold nanostar core solution is placed in a reaction vessel, the pH is adjusted to 12-14, a sulfur source and a metal sulfide precursor are added to the solution to react, and after the reaction, the solution is centrifuged and washed, and freeze-dried to obtain a first gold nanostar with a core-shell structure; The gold nanostar core solution is placed in a reaction container, the pH is adjusted to 12-14, a reducing agent and a metal oxide precursor are added to the solution for reaction, and after the reaction, the solution is centrifuged and washed, and freeze-dried to obtain a second gold nanostar with a core-shell structure.

5. The method for preparing core-shell gold nanostars according to claim 4, characterized in that: The sulfur source includes thiourea, and the metal sulfide precursor includes ferrous chloride; the mass ratio of the gold nanostar core to ferrous chloride is (3.5-4.5):

1.

6. The method for preparing core-shell gold nanostars according to claim 4, characterized in that: The reducing agent includes ascorbic acid, the metal oxide precursor includes copper chloride; the mass ratio of the gold nanostar core to copper chloride is (3-4):

1.

7. The method for preparing core-shell gold nanostars according to claim 4, characterized in that: The preparation method of the gold nanostar core solution comprises: (1) Mixing chloroauric acid solution and sodium citrate solution at 90-110°C to generate spherical gold nanoparticles; (2) mixing the spherical gold nanoparticles with chloroauric acid, silver nitrate, and hydrochloric acid solution, adding ascorbic acid under stirring conditions for reduction reaction, and then adding PVP to stabilize the morphology; (3) The reaction product is centrifuged to remove unreacted substances, and the gold nanostar core solution is obtained after repeated washing.

8. The method for preparing core-shell gold nanostars according to claim 7, characterized in that: In step (1), the molar ratio of chloroauric acid to sodium citrate is 1:(12-14); in step (2), the mass ratio of the spherical gold nanoparticles, silver nitrate and chloroauric acid is 1:(9-11):(45-55).

9. Use of the core-shell gold nanostar according to claim 1 in detecting antioxidants, characterized in that: The antioxidant includes any one or a combination of two or three of ascorbic acid, glutathione, cysteine, gallic acid, tannic acid, uric acid, sodium citrate, and caffeic acid.

10. The use according to claim 9, characterized in that The antioxidant detection method includes the following steps: Based on a buffer, a color developing agent, and an oxidizing agent, a first detection solution containing the first gold nanostar and a second detection solution containing the second gold nanostar are prepared respectively; Respectively reacting the first detection liquid and the second detection liquid with the antioxidant to be tested, measuring the absorbance change of the reaction system at preset time points, and obtaining absorbance data at multiple time points; A multidimensional data matrix was constructed based on the absorbance data, and the data matrix was processed using multivariate statistical analysis methods to distinguish the types of antioxidants; The mass ratio of the first gold nanostar to the second gold nanostar is 1:(1-2).

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