A micron-sized gold nanosheet, preparation method and application thereof

Abstract

The invention belongs to the technical field of nano-gold sheets, and discloses a micron-sized gold nano-sheet, a preparation method and an application thereof. The preparation method of the micron-sized gold nano-sheet comprises: step one, based on the addition of no reducing agent, applying an appropriate amount of ethylenediaminetetraacetic acid chelating agent; step two, under the action of an appropriate amount of ethylenediaminetetraacetic acid chelating agent, preparing a micron-sized single crystal nano-gold sheet by a hydrothermal synthesis method, and demonstrating its application in the field of catalysis and the field of surface enhanced Raman scattering (SERS). The micron-sized gold nano-sheet prepared by the preparation method of the micron-sized gold nano-sheet is applied in the field of catalysis and the field of surface enhanced Raman scattering (SERS). The invention can not only facilitate the preparation of micron-sized single crystal gold nano-sheets, but also demonstrates that the nano-gold sheet has excellent catalytic activity and surface enhanced Raman scattering activity.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-gold flakes, and in particular relates to a micron-level gold nano-flake, a preparation method and an application thereof. Background Art

[0002] At present, there are still great difficulties in the preparation of micron-sized gold nanosheets with existing technologies. There are relatively few reports on micron-sized sheets. For example, only Wang Jin'e and Pei Renjun, researchers from the Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, have synthesized micron-sized ultra-thin MOF sheets with the help of benzoic acid. Jing Aihua, Ma Xiaoyuan and others used the reducibility of agarose to synthesize a large number of micron-sized single-crystalline gold nanosheets with a side length of several microns in situ in agarose gel. However, there are no literature reports on the preparation of micron-sized nano-gold sheets based on the addition of no reducing agent. Therefore, the preparation of micron-sized nano-gold sheets based on chelating agents and no additional addition of reducing agents is very innovative. However, there are few reports on the application of micron-sized nano-gold sheets in the field of catalysis. In addition, this method does not use organic toxic and harmful reagents, and is a green synthesis method, which provides a new idea for the green synthesis of micro-nanostructured materials. Generally, it is easier to prepare nano-sized colloidal gold by chemical reduction, but there are still relatively large difficulties in synthesizing micron-sized gold nanosheets.

[0003] Through the above analysis, the problems and defects of the prior art are as follows: There are relatively great difficulties in synthesizing micron-sized gold nanosheets in the prior art. For example, from the perspective of the synthesis process of gold nanosheets, the existing methods often require surfactants (and) or reducing agents to achieve the preparation of nanogold sheets, and the yield of synthesized nanogold sheets is not high. In 2016, Chen et al. reported that in the presence of a surfactant (CTAB), ascorbic acid was used as a reducing agent to achieve the preparation of hexagonal nanogold sheets with a thickness of about 114nm and a side length of about 3.5μm, with a maximum yield of about 60% (DOI: 10.1007 / s40820-016-0092-6). Organic solvents, especially polyols, are widely used in hydrothermal high-temperature synthesis of nano-gold particles. For example, Lee et al. synthesized various trihedral, tetrahedral and hexahedral nano-gold materials with PVP and chloroauric acid in ethylene glycol solution in 2008 (DOI: 10.1021 / cg0702075). However, the nano-gold materials prepared by this method need to be cleaned and purified by ethylene glycol before application, which is not conducive to the rapid and convenient application of nano-gold structural materials. Therefore, in terms of the safety of the reagents used, the convenience of the synthesis process and the effectiveness of the application, the nano-gold flakes prepared by the present invention are very innovative.

[0004] The difficulty of solving the above problems and defects is: the synthesis of micron-sized gold nanosheets is not just a conceptual change from nanometer to micrometer. It is often necessary to consider multiple conditions such as the type of reaction reagents, the temperature of the reaction, the pH value and the time. Chelating agents or complexing agents are often used in mineral flotation processes, hydrometallurgy, extraction and separation of metal elements, softening and dyeing of water, etc., and there are few reports on the use of chelating agents for the preparation of nanostructures. In addition, chelating agents are often not used in the preparation of nanostructures and cannot prepare nanostructures. The present invention adopts chelating agents and combines hydrothermal conditions to achieve the preparation of micron-sized nanosheets, which is not only an innovation in the concept of nano preparation, but also an innovation in the new application of chelating agents, and also has innovations in the catalysis and SERS applications of nanosheets.

[0005] The significance of solving the above problems and defects is: synthesizing micron-sized gold nanoflakes has effectively solved the breakthrough from nanometer to micrometer scale, and has also built a bridge for the transition from micro to macro, laying the foundation for the application of micron-sized gold nanoflakes and providing new ideas. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a micron-sized gold nanosheet, a preparation method and an application thereof.

[0007] The present invention is achieved by a method for preparing a micron-sized gold nanosheet, the method comprising:

[0008] Step 1, based on the addition of no reducing agent, applying an appropriate amount of ethylenediaminetetraacetic acid chelating agent;

[0009] Step 2: Under the action of ethylenediaminetetraacetic acid chelating agent, micron-sized single-crystalline nanogold flakes are prepared by hydrothermal synthesis, and their application in the fields of catalysis and surface enhanced Raman scattering (SERS) is demonstrated.

[0010] Further, the step 1 includes: preparing a 1% HAuCl4 aqueous solution as a reserve solution for standby use; preparing 0.2M, 0.5M and 1M NaOH aqueous solutions as reserve solutions respectively, weighing 0.7305g EDTA and dissolving it in 25mL NaOH reserve solution to obtain a 0.1M EDTA NaOH aqueous solution for standby use;

[0011] Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10 mL. Take 10 mL of 1 mM HAuCl4 aqueous solution and put it into a 25 mL polytetrafluoroethylene-lined high-pressure digestion tank; then add 10 μL of 0.1 M EDTA NaOH aqueous solution; shake well and put it into the hydrothermal synthesis reactor.

[0012] Further, the step 2 comprises: heating the drying oven to an appropriate temperature in advance, placing the hydrothermal synthesis reactor in the drying oven, standing for 1 hour, waiting for the reaction to end and turning off the power of the drying oven, waiting for the hydrothermal synthesis reactor to cool to room temperature, opening the polytetrafluoroethylene liner to collect the gold nanosheet aqueous solution for standby use;

[0013] Another object of the present invention is to provide a micron-sized gold nanosheet prepared by the method for preparing the micron-sized gold nanosheet. The size of the gold nanosheet can be adjusted. For example, under different temperature conditions, the thickness of the nano-sized gold sheet can be changed from 50 to 320 nm, and the side length of the sheet can be changed from 3 to 12 μm, with a relatively wide tunable range. This ensures that its physical and chemical properties are more outstanding and its application range is wider.

[0014] Another object of the present invention is to provide an application of the micron-sized gold nanosheet in a catalyst. The catalytic process of the nano-gold sheet on the model reaction is quite rapid, which is conducive to its application in the catalytic reaction.

[0015] Further, it includes: using the reduction of 4-nitrophenol to 4-aminophenol as a model reaction for application demonstration;

[0016] Prepare 10 mM 4-nitrophenol for later use; prepare 0.1 M NaBH4 for later use;

[0017] Take 40 μL of 10 mM 4-nitrophenol and dilute it into 0.2 mM 4-nitrophenol aqueous solution, take 2 mL of 0.2 mM 4-nitrophenol aqueous solution for UV-visible spectrum measurement; then add 800 μL of freshly prepared 0.1 M NaBH4 aqueous solution, the 4-nitrophenol aqueous solution immediately turns light yellow, and the UV-visible spectrum measurement is performed; then take 10 μL of gold nanoflakes aqueous solution as a catalyst and add it to the light yellow mixed solution of 4-nitrophenol and NaBH4, and immediately perform UV-visible spectrum measurement; at the same time, repeat the UV-visible spectrum scan every 2 minutes, and record the change of the absorbance value at the maximum spectral peak position.

[0018] Another object of the present invention is to provide an application of the micron-sized gold nanosheet in surface enhanced Raman scattering.

[0019] Furthermore, the application was demonstrated using crystal violet as a probe molecule;

[0020] Prepare 0.1 mM crystal violet CV for later use;

[0021] Take 100 μL of the gold nanosheet aqueous solution and add 10 μL of 10 -5 Crystal violet aqueous solution, mixed evenly and then subjected to surface enhanced Raman scattering test. The test used 633nm as the excitation wavelength and the spectrum collection range was 500-1800cm-1 , integration time 5s, repeated 2 times.

[0022] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: Based on the addition of no reducing agent, the present invention prepares micron-sized single-crystalline gold nanosheets by hydrothermal synthesis under the action of an appropriate amount of ethylenediaminetetraacetic acid (EDTA) chelating agent, and demonstrates its application in the field of catalysis and surface enhanced Raman scattering. It proves that the present invention can not only facilitate the preparation of micron-sized single-crystalline gold nanosheets, but also illustrates that the nano-gold sheet has excellent catalytic activity and SERS activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention provides a flow chart of a method for preparing micron-sized gold nanosheets.

[0024] Figure 2 It is a schematic diagram of a relatively thin gold nanosheet provided in an embodiment of the present invention.

[0025] Figure 3 It is a schematic diagram of a thicker gold nanosheet provided in an embodiment of the present invention.

[0026] Figure 4 It is a schematic diagram of micron-sized gold nanoflower-like particles provided by an embodiment of the present invention.

[0027] Figure 5 This is the XRD diffraction pattern of the single crystal nano-gold flakes provided in the embodiment of the present invention.

[0028] Figure 6 This is a diagram showing the catalytic effect of 10 μL of single-crystal gold nanosheets provided in an embodiment of the present invention on 4-nitrophenol.

[0029] Figure 7 This is a diagram showing the surface enhanced Raman scattering effect of single crystal gold nanosheets on crystal violet provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] In view of the problems existing in the prior art, the present invention provides a micron-sized gold nanosheet, a preparation method and an application thereof. The present invention is described in detail below in conjunction with the accompanying drawings.

[0032] The method for preparing the micron-sized gold nanosheets provided by the present invention can also be implemented by other steps by ordinary technicians in the industry. Figure 1The method for preparing the micron-sized gold nanosheets provided by the present invention is only a specific embodiment.

[0033] like Figure 1 As shown, the method for preparing micron-sized gold nanosheets provided in an embodiment of the present invention comprises:

[0034] S101: Based on the addition of no reducing agent, an appropriate amount of ethylenediaminetetraacetic acid (EDTA) chelating agent is added;

[0035] S102: Micrometer-sized single-crystalline gold nanosheets were prepared by hydrothermal synthesis under the action of an appropriate amount of ethylenediaminetetraacetic acid (EDTA) chelating agent, and their application in the field of catalysis was demonstrated.

[0036] S103: Micrometer-sized single-crystalline gold nanosheets were prepared by hydrothermal synthesis under the action of ethylenediaminetetraacetic acid chelating agent (EDTA), and their applications in catalysis and surface enhanced Raman scattering (SERS) were demonstrated.

[0037] In step S101, an appropriate amount of ethylenediaminetetraacetic acid (EDTA) chelating agent is applied without adding a reducing agent;

[0038] Prepare 1% HAuCl4 aqueous solution as stock solution for later use; prepare 0.2M, 0.5M and 1M NaOH aqueous solutions as stock solutions respectively, weigh 0.7305g EDTA and dissolve it in 25mL NaOH stock solution to obtain 0.1M EDTA NaOH aqueous solution for later use;

[0039] Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10 mL. Take 10 mL of 1 mM HAuCl4 aqueous solution and put it into a 25 mL polytetrafluoroethylene-lined high-pressure digestion tank; then add 10 μL of 0.1 M EDTA NaOH aqueous solution; shake well and put it into the hydrothermal synthesis reactor.

[0040] In step S102, the drying oven is heated to an appropriate temperature in advance, the hydrothermal synthesis reactor is placed in it, and it is left to stand for 1 hour, waiting for the reaction to end while turning off the power of the drying oven, and when the hydrothermal synthesis reactor is cooled to room temperature, the polytetrafluoroethylene lining is opened to collect the gold nanosheet aqueous solution for use.

[0041] The micron-sized gold nanosheets of the present invention are applied in the fields of catalysis and surface enhanced Raman scattering, including:

[0042] Micron-sized gold nanosheets are used in the field of catalysis, with the reduction of 4-nitrophenol to 4-aminophenol as a model reaction for application demonstration;

[0043] Prepare 10 mM 4-nitrophenol for later use; prepare 0.1 M NaBH4 for later use;

[0044] Take 40 μL of 10 mM 4-nitrophenol and dilute it into 0.2 mM 4-nitrophenol aqueous solution, take 2 mL of 0.2 mM 4-nitrophenol aqueous solution for UV-visible spectrum measurement; then add 800 μL of freshly prepared 0.1 M NaBH4 aqueous solution, the 4-nitrophenol aqueous solution immediately turns light yellow, and the UV-visible spectrum measurement is performed; then take 10 μL of gold nanosheet aqueous solution as a catalyst and add it to the light yellow mixed solution of 4-nitrophenol and NaBH4, and immediately perform UV-visible spectrum measurement; at the same time, perform repeated UV-visible spectrum scanning every 2 minutes, and record the change of absorbance value at the maximum spectral peak position;

[0045] The micron-sized gold nanosheets of the present invention are applied in the field of surface enhanced Raman scattering, and crystal violet is used as a probe molecule for application demonstration;

[0046] Prepare 0.1 mM crystal violet (CV) for later use;

[0047] Take 100 μL of the gold nanosheet aqueous solution and add 10 μL of 10 -5 Crystal violet aqueous solution, mixed evenly and then subjected to surface enhanced Raman scattering test. The test used 633nm as the excitation wavelength and the spectrum collection range was 500-1800cm -1 , integration time 5s, repeated 2 times.

[0048] The technical solution of the present invention is described in detail below in conjunction with experiments.

[0049] like Figure 2-Figure 4 As shown, single-crystalline gold nanosheets were synthesized under different reaction conditions.

[0050] like Figure 5 Shown is the XRD diffraction of single-crystalline gold nanoflakes.

[0051] like Figure 6 As shown, the catalytic effect of 10 μL of single crystal gold nanosheets on 4-nitrophenol.

[0052] like Figure 7 As shown, the surface enhanced Raman scattering effect of single crystal gold nanosheets on crystal violet.

[0053] Through the above experiments, the present invention can not only facilitate the preparation of micron-scale single-crystal gold nanosheets, but also demonstrates that the nano-gold sheets have excellent catalytic activity and surface-enhanced Raman scattering activity.

[0054] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0055] Example 1

[0056] Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10mL. Take 10mL of 1mM HAuCl4 aqueous solution and put it into a 25mL polytetrafluoroethylene-lined high-pressure digestion tank. Then add 10μL of 0.1M EDTA NaOH aqueous solution (NaOH concentration is 0.5M). Shake well and put it into a hydrothermal synthesis reactor. Place it in a drying oven at 100℃ for 1h. After the hydrothermal reactor cools to room temperature, collect the product for characterization and application analysis.

[0057] Only the temperature of the drying oven was changed, and the rest of the process was the same, and the same amount of reactants were placed in the drying oven at 110℃, 120℃, 130℃, 140℃, 150℃ and 160℃ for 1h. After the hydrothermal reactor was cooled to room temperature, the products were collected for characterization and application analysis.

[0058] Example 2

[0059] Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10mL. Take 10mL of 1mM HAuCl4 aqueous solution and put it into a 25mL polytetrafluoroethylene-lined high-pressure digestion tank. Then add 10μL of 0.1M EDTA NaOH aqueous solution (NaOH concentration is 0.5M). Shake well and put it into a hydrothermal synthesis reactor. Place it in a drying oven at 100℃ for 1h. After the hydrothermal reactor cools to room temperature, collect the product for characterization and application analysis.

[0060] Only the reaction time was changed, and the rest of the process was the same, and the same amount of reactants were placed in a drying oven at 110°C for 1h, 2h and 3h. After the hydrothermal reactor was cooled to room temperature, the products were collected for characterization and application analysis.

[0061] Example 3

[0062] Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10mL. Take 10mL of 1mM HAuCl4 aqueous solution and put it into a 25mL polytetrafluoroethylene-lined high-pressure digestion tank. Then add 10μL of 0.1M EDTA NaOH aqueous solution (NaOH concentration is 0.5M). Shake well and put it into a hydrothermal synthesis reactor. Place it in a drying oven at 100℃ for 1h. After the hydrothermal reactor cools to room temperature, collect the product for characterization and application analysis.

[0063] Only the NaOH concentration was changed to change the pH value of the reaction. The rest of the process was the same, with the NaOH concentration being 0.2 M and 1 M, and the reaction was carried out in a drying oven for 1 h. After the hydrothermal reactor was cooled to room temperature, the product was collected for characterization and application analysis.

[0064] Example 4

[0065] Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10mL. Take 10mL of 1mM HAuCl4 aqueous solution and put it into a 25mL polytetrafluoroethylene-lined high-pressure digestion tank. Then add 10μL of 0.1M EDTA NaOH aqueous solution (NaOH concentration is 0.5M). Shake well and put it into a hydrothermal synthesis reactor. Place it in a drying oven at 100℃ for 1h. After the hydrothermal reactor cools to room temperature, collect the product for characterization and application analysis.

[0066] Only the amount of EDTA added was changed, and the rest of the process was the same. 5 μL, 20 μL, and 50 μL of 0.1 M EDTA NaOH aqueous solution (NaOH concentration was 0.5 M) were added respectively, and the reaction was carried out in a drying oven at 110°C for 1 h. After the hydrothermal reactor was cooled to room temperature, the products were collected for characterization and application analysis.

[0067] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the field of the present invention within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing micron-sized gold nanosheets, characterized in that: The preparation method of the micron-sized gold nanosheet comprises: Step 1, based on the addition of no reducing agent, applying an appropriate amount of ethylenediaminetetraacetic acid chelating agent; Step 2: Under the action of ethylenediaminetetraacetic acid chelating agent, micrometer-sized single-crystalline nano-gold flakes are prepared by hydrothermal synthesis, and their application in the fields of catalysis and surface enhanced Raman scattering (SERS) is demonstrated; The step 1 comprises: preparing a 1% HAuCl4 aqueous solution as a stock solution for standby use; preparing 0.2M, 0.5M and 1M NaOH aqueous solutions as stock solutions respectively, weighing 0.7305 g EDTA and dissolving it in 25 mL of the NaOH stock solution to obtain a 0.1M EDTA NaOH aqueous solution for standby use; Take 415 microliters of 1% HAuCl4 aqueous solution and dilute it to 10 mL. Take 10 mL of 1 mM HAuCl4 aqueous solution and put it into a 25 mL polytetrafluoroethylene-lined high-pressure digestion tank. Then add 10 μL of 0.1 M EDTA NaOH aqueous solution. Shake well and put it into the hydrothermal synthesis reactor.

2. The method for preparing micron-sized gold nanosheets according to claim 1, wherein: The step 2 comprises: heating the drying oven to an appropriate temperature in advance, placing the hydrothermal synthesis reactor in the drying oven, standing for 1 hour, waiting for the reaction to end while turning off the power of the drying oven, waiting for the hydrothermal synthesis reactor to cool to room temperature, opening the polytetrafluoroethylene liner, and collecting the gold nanosheet aqueous solution for standby use.

3. A micron-sized gold nanosheet prepared by the method for preparing micron-sized gold nanosheet according to claim 1.

4. Use of the micron-sized gold nanosheets as claimed in claim 3 in catalysts.

5. The use of the micron-sized gold nanosheets in a catalyst as claimed in claim 4, characterized in that: include: The application was demonstrated using the reduction of 4-nitrophenol to 4-aminophenol as a model reaction; Prepare 10 mM 4-nitrophenol for later use; prepare fresh 0.1 M NaBH4 for later use; Take 40 μL of 10 mM 4-nitrophenol and dilute it into 0.2 mM 4-nitrophenol aqueous solution, take 2 mL of 0.2 mM 4-nitrophenol aqueous solution for UV-visible spectrum measurement; then add 800 μL of freshly prepared 0.1 M NaBH4 aqueous solution, the 4-nitrophenol aqueous solution immediately turns light yellow, and the UV-visible spectrum measurement is performed; then take 10 μL of gold nanoflakes aqueous solution as a catalyst and add it to the light yellow mixed solution of 4-nitrophenol and NaBH4, and immediately perform UV-visible spectrum measurement; at the same time, repeat the UV-visible spectrum scan every 2 minutes, and record the change of the absorbance value at the maximum spectral peak position.

6. Use of the micron-sized gold nanosheets as claimed in claim 3 in surface enhanced Raman scattering.

7. The use of the micron-sized gold nanosheets in surface enhanced Raman scattering as claimed in claim 6, characterized in that: Application demonstration using crystal violet as a probe molecule; Prepare 0.1 mM crystal violet CV for later use; Take 100 μL of the gold nanosheet aqueous solution and add 10 μL of 10 -5 Crystal violet aqueous solution was mixed evenly and then subjected to surface enhanced Raman scattering test; the test used 633nm as the excitation wavelength and the spectrum acquisition range was 500-1800 cm -1 , integration time 5s, repeated 2 times.

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