Preparation and performance improvement method of silver dendritic crystal SERS (Surface Enhanced Raman Scattering) substrate by utilizing plasma

Abstract

The invention belongs to the technical field of material preparation and treatment, and particularly relates to a method for preparing and improving the performance of a silver dendritic crystal SERS (Surface Enhanced Raman Scattering) substrate by utilizing plasma. The preparation method comprises the following steps: firstly, preparing a silver dendritic crystal SERS substrate by using a plasma electrochemical method, then treating by using dielectric barrier discharge (DBD) plasma, and modifying the silver dendritic crystal by optimizing discharge parameters. And the SERS substrate subjected to argon DBD plasma treatment has higher SERS activity.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation and processing, and in particular to a method for preparing a silver dendrite SERS substrate by utilizing plasma and improving the performance thereof. Background Art

[0002] Raman spectroscopy is an analytical technique that analyzes scattered light at frequencies different from the incident light to obtain information related to molecular vibrations and rotations, and is applied to molecular structure research. In 1974, British scholar Fleischmann et al. adsorbed pyridine molecules on the surface of a rough silver electrode and discovered the surface-enhanced Raman scattering (SERS) effect for the first time. Surface-enhanced Raman scattering (SERS) can enhance conventional Raman scattering signals by several orders of magnitude. Electromagnetic enhancement and chemical enhancement are the two recognized enhancement mechanisms. The electromagnetic enhancement mechanism plays a dominant role because localized surface plasmons are generated on the surface of noble metals, which effectively amplify the photoelectric field at certain specific locations in the nanostructure, thereby generating an enhanced Raman signal. The preparation of high-performance SERS-active substrates is a key issue in this field. Gold and silver are the most common noble metals used to prepare SERS-active substrates. Silver dendrites have attracted much attention due to their high specific surface area and abundant nanogaps.

[0003] On the one hand, the use of plasma electrochemical synthesis of nanomaterials has been a rapidly developing technology in recent years. This technology primarily utilizes the transfer of charge and active components at the plasma-liquid interface, transferring the plasma's activity to the precursor, allowing for the rapid synthesis of desired nanoparticles. On the other hand, plasma modification technology involves the activation, oxidation, or functionalization of a material's surface through changes in surface functional groups and morphology after exposure to plasma. Plasma technology is currently widely used in the semiconductor, biomedical, and material modification fields.

[0004] Research on surface Raman enhancement substrates focuses on preparing three-dimensional silver nanostructures (such as three-dimensional silver dendrites) with a well-defined surface structure, uniform distribution, and controlled order as SRES active substrates. Such active substrates not only produce reliable, stable, and uniform SRES signals over a wide dynamic range, but also provide an ideal model for testing SRES theory. For example, patent publication number CN 109975270A, entitled "A Silver Nanoflower Periodic Array SERS Substrate and Preparation Method Thereof," discloses a method for preparing silver nanoflower arrays by photolithographically processing a template. This method overcomes the problem of poor signal uniformity, but still presents certain challenges, such as a complex preparation process and high cost.

[0005] The patent with publication number CN 102181891 B and invention name "Silver nanodendrite surface-enhanced Raman scattering substrate and its preparation method and use" discloses a method of depositing silver nanodendrites on ITO conductive glass using an electrochemical method. The preparation process is simple, fast and low-cost, but its reaction conditions are difficult to accurately control, which may lead to inconsistent experimental results.

[0006] In other traditional electrochemical processes, thin film deposition is caused by the dissolution of the metal foil at the anode or the reduction of cations in the metal salt electrolyte at the cathode. Due to the presence of solid electrodes, the reduction products are difficult to separate in some cases.

[0007] In summary, it is necessary to propose a new method strategy to supplement the shortcomings of existing technologies. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for preparing and modifying a silver nanodendrite surface-enhanced Raman scattering substrate, the method comprising the following steps:

[0009] S1: A positive bias DC high voltage is applied above the electrolyte to form a plasma to drive the chemical reaction. The positive electrode of the power supply is connected to a hollow stainless steel needle suspended above the electrolyte, and the negative electrode is connected to a titanium substrate, which is partially immersed in the electrolyte. The electrolyte is a mixture of silver nitrate and citric acid. Discharge is used to achieve plasma electrochemical uniform deposition of silver nanodendrites.

[0010] S2: Place the prepared silver nanodendrite in the center of a quartz cavity, then place the quartz cavity between the plates of a stationary dielectric barrier plasma discharge device and clamp it, wherein the discharge device uses a quartz plate as a dielectric barrier layer (the material of the dielectric barrier layer can also be other insulating media); inject gas (such as argon, nitrogen, oxygen, etc.) into the quartz cavity; adjust the discharge parameters of the discharge device, and when the gas in the quartz cavity is ionized to a certain extent, plasma discharge is generated, and the generated plasma acts on the silver nanodendrite substrate placed in the quartz cavity to modify it.

[0011] Preferably, in step S1, the stainless steel needle is suspended above the electrolyte, the negative electrode is connected to the titanium substrate, and 2 / 3 of the titanium substrate is immersed in the electrolyte; argon gas is introduced into the stainless steel needle through a gas flow meter, and the gas flow rate is 0.1-1.2NL / min; the power supply is adjusted to output 1-5mA of direct current, and the discharge time is 1-10min.

[0012] Preferably, in the step S2, it further comprises: plasma modification time is 30s-30min, power is turned off after plasma treatment, and the silver nanodendrite substrate is taken out after the temperature stabilizes.

[0013] Preferably, in step S2, gas is injected into the quartz chamber, and the gas flow rate is controlled by a gas flow meter. In the experiment, the gas flow rate is 0.1-5 NL / min.

[0014] Preferably, in step S2, the output voltage of the discharge device is 100V, the frequency is adjusted to achieve uniform and stable discharge in the reaction chamber, and the power of the dielectric barrier discharge plasma is 210-240W.

[0015] Preferably, in step S2, the plasma modification time is 30s-30min.

[0016] The present invention also provides a method for detecting the activity of a modified SERS substrate, the method comprising the following steps:

[0017] S01: The above prefabricated samples and the plasma-treated samples were placed in a -6 Soak in a Rhodamine 6G solution of M for 3 hours, rinse with deionized water, and blow dry with high-purity nitrogen gas;

[0018] S02: Detect the signal of Rhodamine 6G molecules using Raman testing.

[0019] Compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0020] 1) The technical solution of the present invention is to use plasma electrochemistry to prepare a silver dendrite substrate, which has the following advantages: using plasma to replace one of the solid electrodes, on the one hand, plasma has macroscopic electrical neutrality, high conductivity and strong reactivity, and its non-equilibrium characteristics can make reactions that are difficult to occur under thermodynamic equilibrium be realized in a milder environment, and a large number of active free radicals generated by the plasma-liquid reaction can promote the rapid progress of the reaction; on the other hand, the non-contact form of plasma-liquid allows metal particles to nucleate uniformly in the liquid, which is purer than nanoparticles prepared by traditional electrochemistry; using plasma to prepare a silver nanodendrite surface enhanced scattering substrate with low cost, simple operation, orderly and controllable structure, and good substrate stability.

[0021] 2) The present invention uses dielectric barrier discharge (DBD) plasma for treatment, and the SERS activity is enhanced after modification;

[0022] 3) The present invention uses silver nitrate as the silver source for the reaction and citric acid as a surfactant and reducing agent to deposit nanoparticles in a dendritic pattern on the titanium substrate. After the reaction is completed, the silver ions are reduced by the plasma and deposited on the titanium surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1ais a diagram of a device for depositing silver dendrites using plasma electrochemical deposition;

[0024] Figure 1b 2. It is a diagram of an apparatus for treating and modifying a silver dendrite substrate using a high voltage generator and a dielectric barrier discharge plasma according to the present invention;

[0025] Figure 1c Schematic diagram of the present invention using R6G dye immersion to detect Raman activity;

[0026] Figure 2 These are optical photographs of DBD plasmas in different atmospheres under the same exposure conditions;

[0027] Figure 3 is the optical emission spectrum of dielectric barrier discharge in different atmospheres;

[0028] Figure 4 The current-voltage curve and QV Lissajous figure of the plasma of the present invention are shown;

[0029] Figure 5 These are scanning electron microscope images of the original silver dendrite sample and the silver dendrite sample after plasma treatment in different atmospheres of the present invention;

[0030] Figure 6 This is the crystallization of the samples of the present invention after being treated with different plasmas;

[0031] Figure 7 The Raman spectra of the silver dendrite sample and R6G after DBD plasma modification in the example of the present invention.

[0032] Figure numerals: 1. gas flow meter, 2. high-voltage DC generator, 3. high-voltage probe, 4. electrolyte, 20. high-voltage generator, 21. high-voltage electrode, 22. dielectric barrier plate, 23. gas inlet, 24. quartz container, 25. ground electrode, 26. sample, 27. gas outlet.

[0033] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. Specific embodiments

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0035] like Figure 1a As shown in FIG, the present invention is a device diagram for plasma electrochemical deposition of silver dendrites, the device comprising a gas flow meter 1, a high voltage DC generator 2, a high voltage probe 3 and an electrolyte 4; Figure 1bAs shown in FIG, the present invention is a device diagram for treating and modifying a silver dendrite substrate using a high voltage generator and a dielectric barrier discharge plasma, comprising a high voltage generator 20, a high voltage electrode 21, a quartz dielectric barrier plate 22, a gas inlet 23, a quartz container 24, a ground electrode 25, a sample 26, and a gas outlet 27; Figure 1c As shown, Figure 1c Schematic diagram of the present invention using R6G dye immersion to detect Raman activity.

[0036] The preparation of plasma electrochemical silver dendrite substrate includes the following steps:

[0037] (1) A titanium sheet with a size of 2 cm × 1 cm × 1 mm was selected as the substrate and cleaned in sequence with acetone, alcohol, and deionized water under ultrasonic conditions.

[0038] (2) Prepare a plasma electrochemical electrolyte, the electrolyte composition is: 30 mL of silver nitrate (0.01 M) and citric acid (0.02 M) solution.

[0039] (3) A positive bias DC high voltage is applied above the electrolyte to form a plasma. There are two electrodes from a high voltage power supply, the positive electrode is connected to a hollow stainless steel needle, and the negative electrode is connected to a titanium substrate. The inner diameter of the stainless steel needle is about 600 μm, and argon gas is introduced into it for discharge. The gas flow rate is controlled by a gas flow meter. The tip of the stainless steel needle is suspended 2 mm above the solution, and the distance between the substrate and the needle is 3 cm. The experimental setup is as follows Figure 1a The output current of the high-voltage power supply is fixed at 2 mA, the output voltage of the generated plasma is about 5.4 kV, and the discharge time is 5 minutes.

[0040] (4) In the above design, the argon plasma acts as the anode and the electrolyte acts as the cathode. Silver ions in the electrolyte migrate toward the substrate at the cathode end under the action of voltage and react with active substances generated by the plasma-liquid interaction along the way. Silver nitrate serves as the silver source for the reaction, and citric acid serves as a surfactant and reducing agent to cause the nanoparticles to deposit in a dendritic shape on the titanium substrate. After the reaction is completed, the silver ions are reduced by the plasma and deposited on the surface of the titanium sheet.

[0041] Modification of silver dendrite surface-enhanced Raman scattering substrates using dielectric barrier discharge plasma includes the following steps:

[0042] (1) The silver dendrite sample prepared above is placed in the center of a quartz cavity, and then placed between the plates of a stationary dielectric barrier plasma discharge device and clamped, wherein the dielectric barrier plasma discharge device uses a quartz plate as a dielectric barrier layer.

[0043] (2) Gas is injected into the quartz chamber, and the gas flow rate is controlled by a gas flow meter. In the experiment, the gas flow rate is 4 NL / min. The discharge parameters of the equipment are adjusted. When the gas in the sample chamber is ionized to a certain degree, a plasma discharge is generated. The generated plasma acts on the silver dendrite substrate placed in the sample chamber, modifying it.

[0044] (3) In this example, the plasma modification time is 30 min. After the plasma treatment, the power is turned off and the sample is taken out after the temperature stabilizes. According to the atmosphere used during the plasma treatment, the sample is named silver dendrite-x, where x is the atmosphere used during the plasma treatment.

[0045] The silver nanodendrite surface-enhanced Raman substrate is used to detect R6G dye molecules in the solution, and the specific implementation method is as follows:

[0046] The above prefabricated samples and the plasma treated samples were -6 M of Rhodamine 6G solution for 3 hours, rinsed with deionized water, and dried with high-purity nitrogen; Raman testing was used to detect the signal of Rhodamine 6G molecules. Raman testing can detect a group of -1 , 769cm -1 , 1181cm -1 , 1306cm -1 , 1359cm -1 , 1505cm -1 and 1649cm -1 The Raman characteristic peaks of R6G molecules are located at 610 cm -1 The Raman peak intensity at is used to evaluate the performance of the substrate.

[0047] The present invention provides a preparation and modification method for a surface-enhanced Raman scattering substrate based on atmospheric pressure plasma. The outstanding advantages are: the silver dendrite nanostructure on the titanium substrate has a uniform morphology, and reliable, stable and uniform SERS signals can be obtained over a wide range; the substrate is a commercial titanium sheet, which does not require pre-treatment, and the deposition process of the silver dendrites is simple, and the preparation process is convenient and fast.

[0048] like Figure 2 As shown, these are optical photographs of DBD plasmas in different atmospheres under the same exposure conditions. Under the same exposure conditions, the argon dielectric barrier discharge plasma shows a uniform and bright lavender glow, while the nitrogen plasma is composed of numerous blue filamentary discharges. In comparison, the argon plasma doped with 25% oxygen has a weaker brightness. There is a more obvious discharge in the reaction chamber area above that contacts the high-voltage electrode, which is bluish in color and weaker in brightness.

[0049] like Figure 3As shown in the figure, it is the optical emission spectrum of the dielectric barrier discharge used in the present invention, which reflects the optical characteristics of the dielectric barrier discharge: the optical emission spectrum of nitrogen plasma is mainly composed of the second positive system (SPS) of nitrogen molecules (311-380nm) and the first negative system (FNS) of nitrogen molecular ions (around 400nm), corresponding to N2 (C 3 Π g -B 3 Π g )and Argon plasma is primarily composed of the aforementioned nitrogen lines and argon emission lines in the near-infrared region (Ar I lines). In addition, an OH line at 309 nm can be observed. In comparison, the optical emission spectrum of argon plasma doped with 25% oxygen only reveals a faint second positive band of nitrogen molecules, with no other spectral lines. This indicates that the overall degree of ionization of the oxygen-doped argon plasma is low, and aside from the ionization of a small amount of nitrogen molecules from the air, no other significant ionized species are observed.

[0050] like Figure 4 The following are the current-voltage curves and QV Lissajous plots of the plasmas of the present invention, reflecting the electrical characteristics of dielectric barrier discharge: the peak voltage across the electrodes for argon and nitrogen plasmas, as measured by the voltage probe, is approximately 17 kV, while the peak voltage across the electrodes for argon-oxygen plasma is approximately 15 kV. The peak currents for all three plasmas are approximately 0.01 A, and the corresponding average output powers are 142.7 W, 143.5 W, and 121.5 W, respectively. Compared to nitrogen and argon-oxygen plasmas, argon plasma has a moderate average output power, the highest discharge energy within a single discharge cycle, the lowest discharge frequency, and the most uniform discharge. This means that the energy applied per unit area of ​​the substrate is the most uniform and moderate.

[0051] like Figure 5The following are scanning electron microscope images of the original silver dendrite sample and the silver dendrite sample after plasma treatment in different atmospheres. The original silver dendrite structure (silver dendrite) has a trunk length of up to several microns and a width of 60-80nm, and a branch length of 200-600nm and a width of 60-70nm. The sample morphology after argon plasma treatment (silver dendrite - Ar) shows a significant increase in the length and width of the dendrite: the trunk portion is extended to 2-5μm and the width reaches 200nm, and the branch portion is up to 400-800nm ​​in length and approximately 100-130nm in width. The trunk and branches of some dendrite structures are broken to form nanorods. The substrate after nitrogen plasma treatment (silver dendrite - N2) no longer shows the silver dendrite structure. The silver nanoparticles aggregate and recombine to form nanoparticles and nanorod structures. The particles are between 200-300nm wide and aggregate into dumbbell-shaped and chain-like structures. The substrate treated with 25% oxygen + argon plasma (silver dendrite-25% O2) showed a gravel block structure of varying sizes, with a relatively rough surface and pores.

[0052] like Figure 6 As shown in the figure, the crystallization of the samples of the present invention after being treated with different plasmas. Except for the sample treated with oxygen plasma, the other samples all show characteristic peaks located at 2θ=38.12°, 44.28° and 64.43°, which are consistent with the face-centered cubic diffraction data in the standard database card Ag JCPDF#04-0783, and are respectively the (111), (200) and (200) crystal planes of silver; and the four diffraction peaks located at 2θ=38.42°, 40.17°, 53.00° and 70.66° are consistent with the hexagonal crystal system data of the database card Ti JCPDF#44-1294, and are respectively the (001), (101), (102) and (103) crystal planes of the titanium substrate. In addition, diffraction peaks belonging to silver oxide (Ag2O) were observed at 2θ = 32.75° and 37.77° on the sample treated with 25% oxygen + 75% argon plasma, corresponding to the cubic crystal data of the standard database card Ag2O JCPDF#76-1396, indicating that the silver nanoparticles were oxidized after plasma treatment.

[0053] like Figure 7 As shown, the R6G Raman spectra of the silver dendrite sample and the modified silver dendrite after DBD plasma (silver dendrite-Ar, silver dendrite-N2, silver dendrite 25% O2) in the example of the present invention are located at 610cm -1The performance of the SERS substrate was evaluated by the Raman peak intensity at . Compared with the prefabricated silver dendrite sample, the Raman peak intensity of the sample treated with argon plasma (silver dendrite-Ar) increased by about 2 times, indicating that the SERS activity of the substrate was significantly enhanced. The SERS intensity of the sample treated with nitrogen plasma (silver dendrite-N2) was significantly weakened, while the SERS intensity of the sample treated with argon-oxygen plasma (silver dendrite 25% O2) was the lowest. The plasmas of the three atmospheres all changed the nanostructure of silver, thereby affecting the performance of the SERS substrate.

[0054] Example 1

[0055] A 30mL mixture of silver nitrate (0.01M) and citric acid (0.02M) was added to a beaker as an electrolyte. Two-thirds of the titanium substrate was immersed in the electrolyte. The positive electrode of a high-voltage power supply was connected to the titanium sheet, and the negative electrode was connected to a hollow stainless steel needle. The needle was suspended 2mm above the electrolyte, and argon gas was introduced at a flow rate of 0.4NL / min. The power supply was then adjusted to maintain a current of 2mA in the circuit. Silver nanodendrites were deposited on the surface of the titanium sheet. After 5 minutes, the power was turned off.

[0056] The silver dendrite substrate prepared above was placed in a quartz container, sealed with a quartz dielectric barrier sheet, and a high-voltage electrode was placed above the quartz dielectric barrier sheet. Argon gas with a flow rate of 4NL / min was introduced into the quartz container. The power supply output voltage was then adjusted to 100V, and the frequency was adjusted to ensure stable discharge in the reaction chamber. At this time, the power supply frequency was about 8-9kHz, and the output power was about 210-240W. The plasma treatment time was controlled to 30min to obtain a silver dendrite substrate (silver dendrite-Ar) treated with argon plasma.

[0057] The silver dendrite substrate prepared above was used as a Raman detection substrate. -6 Rhodamine 6G solution was used as the probe molecule, and the silver dendrite substrate was immersed in the solution for 3 hours, then rinsed with pure water and dried with nitrogen gas, and then Raman detection was performed (B&W TEK Raman spectroscopy, excitation wavelength of 532 nm, excitation time of 1 s).

[0058] Compared with Comparative Example 1, the silver dendrites prepared by argon plasma showed a stronger Raman characteristic peak at 610 cm -1 The characteristic peak intensity at is about twice that before DBD plasma treatment, indicating that the SERS activity is enhanced after argon plasma modification.

[0059] Comparative Example 1

[0060] A 30mL mixed solution of silver nitrate (0.01M) and citric acid (0.02M) was added to a beaker as an electrolyte, and two-thirds of the titanium substrate was inserted into the electrolyte. The positive electrode of a high-voltage power supply was connected to the titanium sheet, and the negative electrode was connected to a hollow stainless steel needle. The needle was suspended 2mm above the electrolyte, and argon gas was introduced at a flow rate of 0.4NL / min. The power supply was then adjusted to maintain a current of 2mA in the circuit. Silver nanodendrites were deposited on the surface of the titanium sheet. After 5 minutes, the power was turned off to obtain a prefabricated silver dendrite sample (silver dendrite).

[0061] The silver dendrite substrate prepared above was used as a Raman detection substrate. -6 A Rhodamine 6G solution was used as the probe molecule. The silver dendrite substrate was immersed in the solution for 3 hours, then rinsed with pure water and dried with nitrogen. Raman analysis was then performed (B&W TEK Raman spectroscopy, excitation wavelength 532nm, excitation time 1s). Characteristic Raman peaks attributed to the Rhodamine 6G molecule were observed on the silver dendrite substrate.

[0062] Comparative Example 2

[0063] A 30mL mixture of silver nitrate (0.01M) and citric acid (0.02M) was added to a beaker as an electrolyte. Two-thirds of the titanium substrate was immersed in the electrolyte. The positive electrode of a high-voltage power supply was connected to the titanium sheet, and the negative electrode was connected to a hollow stainless steel needle. The needle was suspended 2mm above the electrolyte, and argon gas was introduced at a flow rate of 0.4NL / min. The power supply was then adjusted to maintain a current of 2mA in the circuit. Silver nanodendrites were deposited on the surface of the titanium sheet. After 5 minutes, the power was turned off.

[0064] The silver dendrite substrate prepared above is placed in a quartz container, sealed with a quartz dielectric barrier sheet on top, and a high-voltage electrode is placed above the quartz dielectric barrier sheet. Nitrogen gas with a flow rate of 4NL / min is introduced into the quartz container. The power supply output voltage is then adjusted to 100V, and the frequency is adjusted to ensure stable discharge in the reaction chamber. At this time, the power supply frequency is about 8-9kHz, and the output power is about 210-240W. The plasma treatment time is controlled to 30min to obtain a silver dendrite substrate (silver dendrite-N2) treated with argon plasma.

[0065] The silver dendrite substrate prepared above was used as a Raman detection substrate. -6 Rhodamine 6G solution was used as the probe molecule, and the silver dendrite substrate was immersed in the solution for 3 hours, then rinsed with pure water and dried with nitrogen gas, and then Raman detection was performed (B&W TEK Raman spectroscopy, excitation wavelength of 532 nm, excitation time of 1 s).

[0066] The silver dendrite substrate modified by nitrogen plasma showed a weak Raman characteristic peak at 610 cm -1The characteristic peak intensity at is about 1 / 2 of that before DBD plasma treatment, indicating that the SERS activity is weakened after nitrogen plasma modification.

[0067] Comparative Example 3

[0068] A 30mL mixture of silver nitrate (0.01M) and citric acid (0.02M) was added to a beaker as an electrolyte. Two-thirds of the titanium substrate was immersed in the electrolyte. The positive electrode of a high-voltage power supply was connected to the titanium sheet, and the negative electrode was connected to a hollow stainless steel needle. The needle was suspended 2mm above the electrolyte, and argon gas was introduced at a flow rate of 0.4NL / min. The power supply was then adjusted to maintain a current of 2mA in the circuit. Silver nanodendrites were deposited on the surface of the titanium sheet. After 5 minutes, the power was turned off.

[0069] The silver dendrite substrate prepared above is placed in a quartz container, which is sealed with a quartz dielectric barrier sheet on top, and a high-voltage electrode is placed on top of the quartz dielectric barrier sheet. An argon-oxygen mixed gas (argon + 25% oxygen) with a flow rate of 4NL / min is introduced into the quartz container. Thereafter, the power supply output voltage is adjusted to 100V, and the frequency is adjusted to achieve stable discharge in the reaction chamber. At this time, the power supply frequency is about 8-9kHz, and the output power is about 210-240W. The plasma treatment time is controlled to 30min to obtain a silver dendrite substrate (silver dendrite-25% O2) treated with argon plasma.

[0070] The silver dendrite substrate prepared above was used as a Raman detection substrate. -6 Rhodamine 6G solution was used as the probe molecule, and the silver dendrite substrate was immersed in the solution for 3 hours, then rinsed with pure water and dried with nitrogen gas, and then Raman detection was performed (B&W TEK Raman spectroscopy, excitation wavelength of 532 nm, excitation time of 1 s).

[0071] The silver dendrite substrate modified by argon-oxygen plasma shows an extremely weak Raman characteristic peak, indicating that argon-oxygen plasma modification has a strong side effect on the silver dendrite SERS substrate.

[0072] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0073] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0074] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing and modifying a silver nanodendrite surface-enhanced Raman scattering substrate, characterized in that: The method comprises the following steps: S1: A positive bias DC high voltage is applied above the electrolyte to form a plasma to drive the chemical reaction. The positive electrode of the power supply is connected to a hollow stainless steel needle suspended above the electrolyte, and the negative electrode is connected to a titanium substrate, which is partially immersed in the electrolyte. The electrolyte is a mixture of silver nitrate and citric acid. Discharge is used to achieve plasma electrochemical uniform deposition of silver nanodendrites. S2: placing the prepared silver nanodendrite in the center of a quartz cavity, and then clamping the quartz cavity between the plates of a dielectric barrier plasma discharge device, wherein the discharge device uses a quartz plate as a dielectric barrier layer; injecting gas into the quartz cavity; adjusting the discharge parameters of the discharge device, and generating plasma discharge after the gas in the quartz cavity is ionized to a certain extent, and the generated plasma acts on the silver nanodendrite substrate placed in the quartz cavity to modify it.

2. The method according to claim 1, wherein: In step S1, the positive electrode of the output power supply is connected to a hollow stainless steel needle, which is suspended above the electrolyte, and the negative electrode is connected to the titanium sheet substrate, with 2 / 3 of the titanium sheet substrate immersed in the electrolyte; argon gas is introduced into the stainless steel needle through a gas flow meter, and the gas flow rate is 0.1-1.2NL / min; the power supply is adjusted to output 1-5mA of direct current, and the discharge time is 1-10min.

3. The method according to claim 1, wherein: In the step S2, it also includes: plasma modification time is 30s-30min, turning off the power after the plasma treatment, and taking out the silver nanodendrite substrate after the temperature stabilizes.

4. The method according to claim 1, wherein: In step S2, the discharge atmosphere is injected into the quartz chamber, and the gas flow rate is controlled by a gas flow meter. In the experiment, the gas flow rate is 0.1-5 NL / min.

5. The method according to claim 1, wherein: In step S2, the output voltage of the discharge device is 100V, the frequency is adjusted to achieve uniform and stable discharge in the reaction chamber, and the power of the dielectric barrier discharge plasma is 210-240W.

6. The method according to claim 1, wherein: In the step S2, the plasma modification time is 30s-30min.

7. The method according to claim 1, wherein: In step S2, the material of the dielectric barrier layer is an insulating medium.

8. The method according to claim 1, wherein: In step S2, the gas is argon, nitrogen or oxygen.

9. A method for detecting the activity of the modified SERS substrate obtained in claims 1-8, characterized in that: The method comprises the following steps: S01: The above prefabricated samples and the plasma-treated samples were placed in a -6 Soak in a Rhodamine 6G solution of M for 3 hours, rinse with deionized water, and blow dry with high-purity nitrogen gas; S02: Detect the signal of Rhodamine 6G molecules using Raman testing.

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