CN103172404A - Three-dimensional metal-graphene composite substrate and preparation method thereof - Google Patents

Abstract

The invention discloses a three-dimensional metal-graphene composite substrate and a preparation method thereof. The composite substrate of the present invention is composed of a first nanolayer, a graphene layer and a second nanolayer, wherein the first nanolayer is deposited on the surface of the amorphous carbon substrate, the graphene layer is spin-coated on the surface of the first nanolayer, and the second nanolayer is deposited on the surface of the amorphous carbon substrate. Two nanometer layers are deposited on the surface of the graphene layer, and the first nanometer layer and the second nanometer layer are gold nanometer layer or silver nanometer layer. The invention constructs an active substrate with good surface-enhanced Raman effect, and its preparation method is simple and fast, with high efficiency and low preparation cost.

Description

Three-dimensional metal-graphene composite substrate and preparation method thereof

technical field

The invention relates to a nanoparticle composite material and a preparation method, especially based on a three-dimensional metal-graphene composite structure as a surface-enhanced Raman substrate and a preparation method thereof.

Background technique

 Surface-enhanced Raman spectroscopy (SERS) technology, as a highly sensitive and powerful spectroscopic technique with single-molecule recognition, has proven to have important applications in the fields of analytical chemistry and biomedicine, especially for the detection of biomolecules. For the enhancement mechanism of surface-enhanced Raman scattering, there are two main mechanisms: one is the electromagnetic field enhancement mechanism based on surface plasmon resonance, and the other is the chemical enhancement mechanism based on charge transfer. The detection technology of surface-enhanced Raman spectroscopy can effectively overcome the shortcoming of the detection signal of ordinary Raman spectroscopy being very weak. the

The most important thing in surface-enhanced Raman spectroscopy is to develop active substrates based on noble metal nanostructures to increase the intensity of the Raman signal of probe molecules. At present, the application of gold and silver-based rough metal particles, nanostructure arrays, and colloidal particle solutions in surface-enhanced Raman spectroscopy detection has been realized. Silver nanostructures have the highest surface plasmon resonance energy and the best enhancement effect, but their chemical stability is poor and the surface is easy to oxidize, which is a major weakness of silver nanostructures as surface-enhanced Raman active substrates. Compared with silver, the enhancement effect of gold is slightly lower, but gold has better biocompatibility and chemical stability. Recently, according to the report of NANO letter, graphene materials can also be used as surface-enhanced Raman active substrates. This further facilitates the research on the surface-enhanced Raman activity of noble metal-graphene composites. The combination of graphene and gold (silver) can get a stronger enhanced signal, in which there is a synergy between the chemical enhancement of graphene and the electromagnetic field enhancement of metal nanostructures: the single-layer sheet structure of graphene is conducive to the adsorption of molecules and substrates. Charge transfer at the bottom; gold (silver) nanoparticles will produce different plasmon resonance modes as the distance between particles shrinks. For example, when the nanoparticles are in contact with each other on the plane, the strong coupling effect of the plasma enhances the electromagnetic field strength of the nanoparticles, resulting in the so-called "hot spot". This is the strengthening mechanism of traditional graphene and gold (silver) composite materials as surface-enhanced Raman substrates. At present, there are many methods for preparing substrates with surface-enhanced Raman activity, such as: electrochemical redox roughening method, chemical synthesis method, template method, etc. Each of the above methods has advantages and disadvantages. The process of the chemical redox roughening method is simple, but the surface of the electrode formed is uneven, and the shape and size are not easy to control; the shape and size of the chemically synthesized sol nanoparticles can be controlled, and the enhancement effect is very good, but the added surface Reagents interfere with the enhanced signal, and the preparation process is cumbersome, often requiring multiple centrifugations to remove excess impurities. The template method can obtain an ordered nanoparticle array, but the cost is high, the preparation is relatively complicated, and the Raman signal is relatively weak.

Contents of the invention

The object of the present invention is to provide a three-dimensional metal-graphene composite substrate and a preparation method thereof.

For realizing above object, the technical scheme that the present invention adopts is:

The three-dimensional metal-graphene composite substrate of the present invention is composed of a first nano-layer, a graphene layer and a second nano-layer, the first nano-layer is deposited on the surface of an amorphous carbon substrate, and the graphene layer is spin-coated on the second On the surface of a nanometer layer, the second nanometer layer is deposited on the surface of the graphene layer, and the first nanometer layer and the second nanometer layer are gold nanolayers or silver nanolayers.

Further, the gold nanolayer of the present invention is composed of nanoparticles, and the silver nanolayer has a dendrite structure or a cluster structure. the

Further, the particle size of the nanoparticles of the gold nanolayer in the present invention is 15nm-65nm.

Further, if the silver nanolayer in the present invention is a cluster structure, the diameter of the cluster is 100-150 nm. the

Further, the thickness of the graphene layer in the present invention is 1-8 nm.

Preferably, the gold nanolayer of the present invention is composed of nanoparticles with a particle size of 15nm to 65nm, and the silver nanolayer is in a dendritic structure or a cluster structure; if the silver nanolayer is in a cluster structure, then the The diameter is 100-150 nm; the thickness of the graphene layer is 1-8 nm.

The preparation method of the three-dimensional metal-graphene composite substrate of the present invention comprises the following steps:

(1) On the surface of the amorphous carbon film substrate, the first nanometer layer is deposited by a constant potential electrochemical deposition method;

If the first nano-layer is a gold nano-layer, the deposition conditions are: the electrodeposition solution is a mixed aqueous solution of 0.6-2.4 mmol/L HAuCl ₄ and 0.075-0.1 mol/L KH ₂ PO ₄ , and the deposition time is 300-600 s , the deposition potential is -0.5～-0.8V;

If the first nano layer is a silver nano layer, the deposition conditions are as follows: the electrodeposition solution is a mixed aqueous solution of 3-6 mmol/L _AgNO3 and 0.375-0.5 mol/L _KNO3 , the deposition time is 1200-1600s, and the deposition time is 1200-1600s. The potential is -0.3～-0.5V;

(2) Use a spin coater to drop 40-80 μL of 0.5-1 mg/mL graphene oxide aqueous solution on the surface of the first nanometer layer. 5 seconds to 30 seconds;

(3) The graphene oxide spin-coated on the first nano-layer is reduced to graphene by electrochemical reduction method, the condition of said electrochemical reduction method is: the reduction solution is 20～60mmol/L KH ₂ PO ₄ For aqueous solution, the working mode of the electrochemical workstation is cyclic voltammetry, the reduction potential is -1.5V to 0 V, the scan rate is 50 to 100 mV/s, and the number of cycles is 10 to 60;

(4) Utilize the electrochemical deposition method to deposit the second nanometer layer on the graphene;

If the second nanometer layer is a gold nanolayer, the deposition conditions are: the electrodeposition solution is a mixed aqueous solution of HAuCl ₄ of 0.6-2.4 mmol/L and KH ₂ PO ₄ of 0.075-0.1 mol/L, and the deposition time is 300-600s , the deposition potential is -0.5～-0.8V;

If the second nanometer layer is a silver nanolayer, the deposition conditions are: the electrodeposition solution is a mixed aqueous solution of 3-6 mmol/L _AgNO3 and 0.375-0.5 mol/L _KNO3 , and the deposition time is 1200-1600s. The deposition potential is -0.3～-0.5V.

Further, the amorphous carbon film of the present invention is an amorphous carbon film with tetrahedral structure doped with nitrogen.

Further, the electrochemical workstations of the constant potential electrochemical deposition method and the electrochemical reduction method of the present invention both use a three-electrode system, and the reference electrode in the three-electrode system is a saturated calomel electrode.

In the above steps, graphene oxide is synthesized by the Hummers method; the electrochemical deposition of gold or silver nano-layers and the electrochemical reduction of graphene oxide all use a three-electrode system, the amorphous carbon film is the working electrode, and the platinum sheet is the auxiliary electrode. The calomel electrode is the reference electrode; the amorphous carbon film in step (1) is ultrasonically cleaned successively through acetone, ethanol, and ultrapure water, each solution is cleaned for 5 minutes, and after drying, it is used for electrochemically depositing gold or silver nano-layers. . the

Compared with prior art, the beneficial effect of the present invention is:

1. The substrate of the present invention adopts the three-dimensional composite layer structure of the first nano-layer-graphene layer-the second nano-layer. Such a structure not only has the coupling effect of metal plasma on the plane, but also has a coupling effect in the direction perpendicular to the substrate. Plasma coupling can occur. The graphene layer acts as an electron transport layer to generate an inner layer electric field in the vertical direction. Compared with the traditional Raman active substrate, the substrate of the present invention has greater advantages in enhancing the Raman scattering intensity.

2. In the present invention, due to adopting the three-dimensional composite layer structure of the first nano-layer-graphene layer-the second nano-layer, when the first nano-layer is a silver nano-layer, it can play a certain role in silver that is easy to oxidize. Protective effects.

3. The present invention adopts the electrochemical deposition method to prepare gold nanolayer or silver nanolayer, which is easier to control the shape and size of the nanolayer than the electrochemical roughening method, and saves chemical reagents and preparation procedures than the chemical synthesis method, and there will be no Surfactant interferes with the detection, the preparation efficiency is higher, and the Raman signal is stronger.

4. When the first nanolayer and the second nanolayer of the substrate of the present invention are both gold nanolayers, the substrate has good chemical stability and good biocompatibility, and can be used for the detection of biomolecules.

Description of drawings

1-3 are scanning electron micrographs of three stages in the preparation process of the gold nanoparticle-graphene-gold nanoparticle surface-enhanced Raman active substrate in Example 1. Wherein, Fig. 1 is the scanning electron micrograph of the gold nanoparticle layer deposited on the surface of the amorphous carbon film; Fig. 2 is the scanning electron micrograph of graphene covering the gold nanoparticle layer; Fig. 3 is the gold nanoparticle-graphene-gold nanoparticle SEM image.

4 is a scanning electron micrograph of the surface-enhanced Raman active substrate of the silver nanodendrimer-graphene-gold nanoparticle of Example 2.

5 is a scanning electron microscope image of the surface-enhanced Raman active substrate of gold nanoparticles-graphene-silver nanoclusters in Example 3.

6-8 are reduction characterization diagrams of the graphene oxide described in the present invention. Wherein, Fig. 6 is an electrochemical reduction curve of graphene oxide; Fig. 7 is an X-ray photoelectron spectrum diagram of graphene oxide and graphene; Fig. 8 is a Raman spectrum diagram of graphene oxide and graphene.

Fig. 9 is the Raman spectrum of rhodamine B adsorbed on the surface-enhanced Raman active substrate in steps (2) and (3) of Example 1. (a) is the Raman signal of Rhodamine B detected on the substrate prepared in step (2) that is only covered with a gold nanoparticle layer but without a graphene layer; (b) is covered with graphene in step (3) The Raman signal of rhodamine B detected by the gold nanoparticles in the layer; (c) is the Raman signal of rhodamine B detected by the surface-enhanced Raman active substrate of three-dimensional gold nanoparticles-graphene-gold nanoparticles.

Fig. 10 is a Raman spectrum of rhodamine B adsorbed on the surface-enhanced Raman active substrate of the three-dimensional metal-graphene composite structure in the present invention. Curves (a), (b), and (c) represent the surface enhancement of gold nanoparticles-graphene-gold nanoparticles, silver nanodendrites-graphene-gold nanoparticles, gold nanoparticles-graphene-silver nanoclusters, respectively Raman signal of rhodamine B detected by Raman active substrate.

Detailed ways

Example 1:

In this embodiment, the three-dimensional metal-graphene composite substrate of the present invention is prepared according to the following steps:

(1) The amorphous carbon film was ultrasonically cleaned with acetone, ethanol, and ultrapure water in sequence, each solution was cleaned for 5 minutes, and dried for electrochemical deposition of gold nano-layers. the

(2) A gold nanoparticle layer was deposited on the surface of the amorphous carbon film by electrochemical deposition, and the electrodeposition solution used was a mixed aqueous solution of 20ml 0.6 mmol/L HAuCl ₄ and 0.075 mol/L KH ₂ PO ₄ . A three-electrode system was adopted: the amorphous carbon film was used as the working electrode, the platinum sheet was used as the auxiliary electrode, and the saturated calomel electrode was used as the reference electrode. The model of the electrochemical workstation is CHI630D, the working mode is the constant potential mode, and the deposition is at -0.8V for 600 seconds. Samples were dried for later use. The scanning electron microscope image of the sample is shown in Figure 1. It can be seen from Figure 1 that the deposited gold nanoparticles are relatively uniform, and the particle diameter is 65nm.

(3) Graphene oxide was spin-coated on the sample prepared in step (2) using a spin coater. The specific process is as follows: Take 40 μL of 0.5 mg/mL graphene oxide, drop it on the sample prepared in step (2), adjust the spin-coating speed to 500 rpm, and the spin-coating time to 5 seconds. After the spin coating is completed, use the electrochemical workstation to perform electrochemical reduction on the sample spin-coated with graphene oxide. The reduction solution is 20mL 20 mmol/L KH ₂ PO ₄ aqueous solution, the working mode is cyclic voltammetry, and the parameter is -1.5V Cycle 10 cycles from 0 V to 100 mV/s at a rate of 100 mV/s to obtain a graphene-covered gold nanoparticle layer sample. The SEM image of the sample is shown in Figure 2. It can be seen from FIG. 2 that the graphene is covered on the gold nanoparticle layer, and the thickness is between 1 and 8 nm.

(4) After the reduction of graphene oxide is completed, on the sample obtained in step (3), use the same deposition conditions in the process of step (2) to redeposit gold nanoparticles. The prepared three-dimensional metal-graphene composite substrate is composed of gold nanolayer-graphene-gold nanolayer. The SEM image of the substrate is shown in Figure 3. It can be seen from Figure 3 that the distribution of gold nanoparticles is denser than that in Figure 1, and the particle size is 15-65nm.

(5) Characterize the graphene covered on the gold nanoparticle layer, and the results are shown in Figure 6. Figure 6 is the electrochemical reduction curve of graphene oxide. It can be seen that there is a reduction current peak at -0.8V, which is the performance of graphene oxide being reduced.

(6) Using rhodamine B as a probe molecule, characterize the three-dimensional metal-graphene composite substrate and test the surface-enhanced Raman performance, and use the gold nanoparticle layer prepared in step (2) and step (3) to prepare A sample of gold nanoparticles covered with graphene was used as a comparison group. The specific operation is as follows: (a) soak the three-dimensional metal-graphene composite substrate in a 10 ^-6 mol/L rhodamine B aqueous solution for 24 hours; (b) take out the substrate, rinse it with ultrapure water, and vacuum Dry it in a drying oven at room temperature for 1 hour, and then use it for Raman detection (the test results are shown in Figure 9). As can be seen from Fig. 9, it is obvious that the Raman signal of Rhodamine B on the surface-enhanced Raman substrate of the three-dimensional metal-graphene composite structure obtained in this embodiment (i.e. gold nanoparticles-graphene-gold nanoparticles three-dimensional structure substrate) is stronger than that of only Raman signal of rhodamine B on samples with gold nanoparticles layer (curve a) and gold nanoparticles covered with graphene (curve b).

Example 2:

In this embodiment, the three-dimensional metal-graphene composite substrate is prepared according to the following steps:

(1) Electrochemically deposit silver nano-layers on the surface of the amorphous carbon film after cleaning in step (1) of Example 1, and the electrodeposition solution is a mixed aqueous solution of 3mmol/L AgNO and _0.375mol /L _KNO . A three-electrode system is adopted: the amorphous carbon film is used as the working electrode, the platinum sheet is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The model of the electrochemical workstation is CHI630D, the working mode is the constant potential mode, and the deposition is at -0.3V for 1200 seconds. Samples were dried for later use.

(2) Graphene oxide is spin-coated on the above-mentioned prepared sample by using a spin coater. The specific process is as follows: take 80uL of 1mg/mL graphene oxide, drop it on the sample prepared in step (1), adjust the spin coating speed to 4000 rpm, and spin coating time to 30 seconds. After the spin coating is completed, use the electrochemical workstation to perform electrochemical reduction on the sample spin-coated with graphene oxide. The reduction solution is an aqueous solution of 20mmol/L KH ₂ PO ₄ . The working mode of the electrochemical workstation is cyclic voltammetry, and the parameter is -1.5 Cycle 60 cycles from V to 0 V at a rate of 50 mV/s.

(3) After the reduction of graphene oxide is completed, the sample prepared in step (2) is subjected to electrochemical deposition of gold nanoparticles, and the electrodeposition solution is a mixed aqueous solution of 2.4 mmol/L HAuCl ₄ and 0.1 mol/L KH ₂ PO ₄ . A three-electrode system was adopted: the amorphous carbon film was used as the working electrode, the platinum sheet was used as the auxiliary electrode, and the saturated calomel electrode was used as the reference electrode. The model of the electrochemical workstation is CHI630D, the working mode is the constant potential mode, and the deposition is carried out at -0.5V for 300 seconds. The prepared three-dimensional metal-graphene composite substrate is composed of silver nanolayer-graphene-gold nanolayer. The scanning electron micrograph of the substrate is shown in Figure 4. As can be seen from Figure 4, the silver nanolayer is in a dendrite structure, and the silver nanolayer, graphene layer and gold nanoparticle layer form a three-layer structure, and the particle diameter of the gold nanoparticle is 15～ 20nm.

(4) Characterize the graphene covered on the silver nanolayer, and the results are shown in Figure 7. Figure 7 is the X-ray photoelectron spectroscopy (XPS) test results of graphene oxide and graphene. It can be seen from Figure 7 that the carbon-oxygen bond peak intensity decreases significantly after the graphene oxide is reduced, indicating that the graphene oxide is reduced. reduction.

(5) Using rhodamine B as a probe molecule, the three-dimensional metal-graphene composite substrate was characterized and the surface-enhanced Raman performance test was performed. The specific operation is as follows: (a) soak the three-dimensional metal-graphene composite substrate in a 10 ^-6 mol/L rhodamine B aqueous solution for 24 hours; (b) take out the substrate, rinse it with ultrapure water, and vacuum Dry in a drying oven at room temperature for 1 hour before using for Raman detection. The test results are shown in curve b of FIG. 10 .

Example 3:

In this embodiment, the three-dimensional metal-graphene composite substrate is prepared according to the following steps:

(1) A gold nano-layer was deposited on the surface of the amorphous carbon film by electrochemical deposition, and the electrodeposition solution was a mixed aqueous solution of 2.4 mmol/L HAuCl ₄ and 0.075 mol/L KH ₂ PO ₄ . A three-electrode system was adopted: the amorphous carbon film was used as the working electrode, the platinum sheet was used as the auxiliary electrode, and the saturated calomel electrode was used as the reference electrode. The model of the electrochemical workstation is CHI630D, the working mode is the constant potential mode, and the deposition is at -0.5V for 600 seconds. After the deposition is complete, the samples are dried and ready for use.

(2) Graphene oxide is spin-coated on the above-mentioned prepared sample by using a spin coater. The specific process is as follows: Take 40 μL of 0.5 mg/mL graphene oxide, drop it on the sample prepared in step (1), adjust the spin coating speed to 4000 rpm, and spin coating time to 30 seconds. After the spin coating is completed, use an electrochemical workstation to perform electrochemical reduction on the sample spin-coated with graphene oxide. The reduction solution is 60mmol/L KH ₂ PO ₄ aqueous solution, the working mode is cyclic voltammetry, and the parameters are -1.5V to 0 V is cycled 60 times at a rate of 100 mV/s.

(3) After the reduction of graphene oxide is completed, the sample prepared in step (2) is subjected to electrochemical deposition of silver nanoclusters, and the electrodeposition solution is a mixed aqueous solution of 6 mmol/L AgNO ₃ and 0.5 mol/L KNO ₃ . A three-electrode system is adopted: the amorphous carbon film is used as the working electrode, the platinum sheet is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The model of the electrochemical workstation is CHI630D, the working mode is the constant potential mode, and the deposition is at -0.5V for 1600 seconds. The prepared three-dimensional metal-graphene composite substrate is composed of gold nanolayer-graphene-silver nanolayer, and its scanning electron micrograph is shown in Figure 5. It can be seen from FIG. 5 that the silver nano-layer is in the form of nano-cluster clusters and is very dense, and the particle size is in the range of 100-150 nm.

(4) Characterize the graphene covered on the gold nanolayer, and the results are shown in FIG. 8 . Figure 8 is a graph of Raman spectra of graphene oxide and graphene. It can be seen from Figure 8 that when graphene oxide is reduced to graphene thickness, the proportion of the D peak representing the aromatic ring SP ² breathing vibration mode increases, indicating that graphene oxide can be reduced by electrochemical methods.

(5) Using rhodamine B as a probe molecule, the three-dimensional metal-graphene composite substrate was characterized and the surface-enhanced Raman performance test was performed. The specific experimental process is as follows: (a) soak the three-dimensional metal-graphene composite substrate in 10 ^-6 mol/L rhodamine B aqueous solution for 24 hours; (b) take out the substrate, rinse it with ultrapure water, and place it in Dry in a vacuum oven at room temperature for 1 hour before using for Raman detection. The test results are shown in curve c of FIG. 10 .

For the surface-enhanced Raman performance test of the three-dimensional metal-graphene composite substrate in Examples 1-3, the test results are shown in Figure 10. It can be seen from FIG. 10 that the three-dimensional metal-graphene composite substrates in Examples 1-3 all have good surface-enhanced Raman properties. Among them, the three-dimensional metal-graphene (curve c) composite substrate (the three-dimensional metal-graphene composite substrate composed of gold nanolayer-graphene-silver nanolayer) in Example 3 has the best reinforcement effect. The second nanolayer of the three-dimensional metal-graphene composite substrate in Example 1 (curve a) and Example 2 (curve b) is a gold nanolayer, which has good stability and biocompatibility.

Claims (9)

1. 3-dimensional metal-Graphene composite substrate, it is characterized in that: formed by the first nanometer layer, graphene layer and the second nanometer layer, described the first nanolayer deposition is on the surface of amorphous carbon substrate, described graphene layer is spin-coated on the surface of the first nanometer layer, described the second nanolayer deposition is on the surface of graphene layer, and described the first nanometer layer and the second nanometer layer are gold nano layer or silver nanoparticle layer.

2. 3-dimensional metal according to claim 1-Graphene composite substrate, it is characterized in that: described gold nano layer is made of nanoparticle, and described silver nanoparticle layer is dendritic structure or Cluster Structures.

3. 3-dimensional metal according to claim 2-Graphene composite substrate, it is characterized in that: the particle diameter of the nanoparticle of described gold nano layer is 15nm～65nm.

4. 3-dimensional metal according to claim 2-Graphene composite substrate, it is characterized in that: if described silver nanoparticle layer Cluster Structures, the diameter of cluster is 100～150nm.

5. 3-dimensional metal according to claim 2-Graphene composite substrate, it is characterized in that: the thickness of described graphene layer is 1～8nm.

6. 3-dimensional metal according to claim 1-Graphene composite substrate, it is characterized in that: the nanoparticle that described gold nano layer is 15nm～65nm by particle diameter consists of, and described silver nanoparticle layer is dendritic structure or Cluster Structures; If described silver nanoparticle layer is Cluster Structures, the diameter of cluster is 100～150nm; The thickness of described graphene layer is 1～8nm.

7. the preparation method of the 3-dimensional metal of any one-Graphene composite substrate in a claim 1 to 6, is characterized in that, comprises the steps:

(1) at the amorphous carbon-film substrate surface, by constant potential electrochemical deposition method deposition the first nanometer layer;

If the first nanometer layer is the gold nano layer, mode of deposition is: electrodeposit liquid is the HAuCl of 0.6～2.4 mmol/L ₄KH with 0.075～0.1 mol/L ₂PO ₄Mixed aqueous solution, depositing time is 300～600s, sedimentation potential is-0.5～-0.8V;

If the first nanometer layer is the silver nanoparticle layer, mode of deposition is: electrodeposit liquid is the AgNO of 3～6 mmol/L ₃KNO with 0.375～0.5 mol/L ₃Mixed aqueous solution, depositing time is 1200～1600s, sedimentation potential is-0.3～-0.5V;

(2) use spin coater 0.5～1 mg/mL graphite oxide aqueous solution of 40～80 μ L to be dropped in the surface of the first nanometer layer, the rotating speed of spin coater be 500 turn/min～4000 turn/min, the spin coating time is 5 seconds～30 seconds;

(3) graphene oxide that uses electrochemical reducing will be spin-coated on the first nanometer layer is reduced into Graphene, and the condition of described electrochemical reducing is: reducing solution is the KH of 20～60mmol/L ₂PO ₄The aqueous solution, the electrochemical workstation operating mode is cyclic voltammetry, reduction potential is-1.5V～0 V, scanning speed is 50～100 mV/s, the circulation number of turns is 10～60 circles;

(4) utilize electrochemical deposition method to deposit the second nanometer layer on described Graphene;

If the second nanometer layer is the gold nano layer, mode of deposition is: electrodeposit liquid is the HAuCl of 0.6～2.4 mmol/L ₄KH with 0.075～0.1 mol/L ₂PO ₄Mixed aqueous solution, depositing time is 300～600s, sedimentation potential is-0.5～-0.8V;

If the second nanometer layer is the silver nanoparticle layer, mode of deposition is: electrocasting/electrodeposition liquid is the AgNO of 3～6 mmol/L ₃KNO with 0.375～0.5 mol/L ₃Mixed aqueous solution, depositing time is 1200～1600s, sedimentation potential is-0.3～-0.5V.

8. preparation method according to claim 7 is characterized in that: described amorphous carbon-film is the amorphous carbon-film of the tetrahedral structure of doping nitrogen.

9. according to claim 7 or 8 described preparation methods, it is characterized in that: the electrochemical workstation of described constant potential electrochemical deposition method and electrochemical reducing all uses three-electrode system, and the reference electrode in described three-electrode system is saturated calomel electrode.

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