A carbon-doped silver composite nanoflower SERS substrate and its preparation method and application

Abstract

The present invention discloses a carbon-doped silver composite nanoflower SERS substrate and a preparation method and application thereof. The preparation method comprises the following steps: step 1, growing a nanoflower structure on the surface of a gallium nitride substrate by a vapor phase chemical deposition method; step 2, performing an amination treatment on the surface of the gallium nitride substrate on which the nanoflower structure is grown; step 3, growing carbon-doped silver composite nanoparticles on the surface of the gallium nitride substrate after the amination treatment. The carbon-doped silver composite nanoflower SERS substrate prepared by the method of the present invention has good hydrophobicity and long-term stability, and has good sensitivity and uniformity in the detection of antibacterial agents.

Description

Technical Field

[0001] The present invention relates to the technical field of Raman spectroscopy detection, and in particular to a carbon-doped silver composite nanoflower SERS substrate and a preparation method and application thereof. Background Art

[0002] Surface enhanced Raman scattering (SERS) technology is widely used in analysis, catalysis, and sensing due to its high precision, fast response, and non-destructive testing. The high precision of this technology is due to the localized surface plasmon resonance of the electromagnetic field generated by precious metal nanoparticles in the nano region. Compared with gold particles, silver nanoparticles can generate stronger resonant electromagnetic fields in the nano region under the irradiation of excitation light, so silver nanoparticles show more excellent SERS characteristics. However, silver is very easy to react with oxygen in the air to undergo oxidation, resulting in the SERS substrate prepared using silver nanomaterials being extremely unstable and having a short lifespan. Therefore, the research and use of SERS on silver nanomaterials have been limited so far.

[0003] The generation of SERS signals requires nanoparticles to generate localized surface plasmon resonances in the nanoregion. The resonance region of the electromagnetic field is also called a "hotspot". However, since the shape, size and enrichment level of metal nanomaterials are related to the formation and optical properties of their hotspots, the currently prepared planar SERS substrates have a certain enhancement effect, but are still unable to better gather the detected substances directly to the location of the hotspot. The wettability and hydrophilicity of the solid surface are special properties of the material, which not only determine the surface roughness of the solid SERS substrate, but also affect whether the detected substance can be better focused on the SERS hotspot on the substrate surface. At present, what people are paying attention to is how to use simple methods to prepare efficient SERS substrates with hydrophobic properties to further improve the sensitivity and stability of SERS detection.

[0004] Therefore, designing and preparing a long-term and highly stable silver nano-surface enhanced Raman scattering substrate that can focus the detected substance on the SERS hotspot and further improve the detection accuracy has very important practical application value. Summary of the invention

[0005] To solve the above technical problems, the present invention provides a carbon-doped silver composite nanoflower SERS substrate and a preparation method and application thereof, so as to achieve the purpose of producing a silver nanostructured SERS substrate with high sensitivity, long-term effectiveness, good stability and reproducibility and hydrophobic properties.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A carbon-doped silver composite nanoflower SERS substrate comprises a gallium nitride nanoflower structure grown on an aluminum oxide substrate and carbon-doped silver composite nanoparticles grown on the surface of the gallium nitride nanoflower structure.

[0008] A method for preparing a carbon-doped silver composite nanoflower SERS substrate comprises the following steps:

[0009] Step 1, growing a gallium nitride nanoflower structure on the surface of an alumina substrate by using a vapor phase chemical deposition method;

[0010] Step 2, performing an amino treatment on the surface of the substrate on which the GaN nanoflower structure is grown;

[0011] Step three, growing carbon-doped silver composite nanoparticles on the surface of the substrate after the amination treatment.

[0012] In the above scheme, the specific method of step one is as follows:

[0013] First, in a low-pressure H2 environment, NH3 and trimethylgallium were introduced to grow a GaN buffer layer on an alumina substrate at 500-550°C, and annealed at 1040°C for 120 seconds. Then, a 2μm undoped GaN layer was grown on the GaN buffer layer at 1000-1040°C.

[0014] Next, a 3nm silicon-doped In layer was grown on the undoped GaN layer at 700°C in a low-pressure N2 environment. x Ga 1-x N, x = 0.15-0.25, forming a rough surface, where the silicon doping content is 1×10 20 / cm 3 ;

[0015] Finally, in a low-pressure N2 environment, NH3 and trimethylgallium were introduced, and unintentionally doped gallium nitride and highly doped gallium nitride were periodically grown at 1000-1040°C, with a growth time of 180 seconds for 5-10 cycles to form a gallium nitride nanoflower structure.

[0016] In the above scheme, the specific method of step 2 is as follows:

[0017] First, place the cleaned GaN nanoflower structure upward and treat it with plasma for 3-10 minutes in an oxygen environment.

[0018] Then, the treated substrate is immersed in an ethanol solution of 3-aminopropyltriethoxysilane for 6 to 12 hours;

[0019] Finally, the substrate was placed in ultrapure water for cleaning for 10 to 30 minutes, taken out and blown dry with nitrogen for later use, thereby achieving amino treatment on the surface of the substrate.

[0020] In a further technical solution, in the ethanol solution of 3-aminopropyltriethoxysilane, the volume ratio of 3-aminopropyltriethoxysilane to ethanol is 5:95.

[0021] In the above scheme, the specific method of step three is as follows:

[0022] First, add 5 mL of 40-50 mM silver nitrate solution into a sealable bottle, then add 5 mL of 10-15 mM hexadecylpyridine solution, observe the color change from colorless to milky white, and stir in a dark environment for 30 minutes, controlling the speed to 400-500 rpm;

[0023] Then, put the substrate after amino treatment into the bottle, and then add 2mL of 1-2M sodium hydroxide solution at one time. The color immediately changes to brown and then black. After obvious precipitation is seen, let it grow in the dark for 6-18 hours.

[0024] Finally, the substrate was taken out, ultrasonically cleaned with ultrapure water, and dried with nitrogen, and the preparation of the carbon-doped silver composite nanoflower SERS substrate was completed.

[0025] Application of a carbon-doped silver composite nanoflower SERS substrate in detecting antibacterial agents.

[0026] Through the above technical solution, the present invention provides a carbon-doped silver composite nanoflower SERS substrate and its preparation method and application, which have the following beneficial effects:

[0027] 1. The carbon-doped silver composite nanoflower SERS substrate prepared by the present invention has an ultra-high specific surface area of ​​the gallium nitride nanoflower structure and good hydrophobicity of the carbon-doped silver composite nanoparticles, which can make the detection substances more effectively aggregate on the SERS surface and effectively enhance the SERS signal;

[0028] 2. The carbon-doped silver composite nanoflower SERS substrate prepared by the present invention has long-term stability due to its good anti-oxidation performance. It can be stored in the air for 8 months while the performance remains above 90%, so it has a longer timeliness.

[0029] 3. The carbon-doped silver composite nanoflower SERS substrate prepared in the present invention has good sensitivity and uniformity in the detection of antibacterial agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0031] Figure 1 This is a scanning electron microscope image of the carbon-doped silver composite nanoflower SERS substrate prepared by the present invention;

[0032] Figure 2 The hydrophobic angle measurement of the carbon-doped silver composite nanoflower SERS substrate prepared by the present invention;

[0033] Figure 3 This is the relationship between the hydrophobicity of the carbon-doped silver composite nanoflower SERS substrate and the SERS signal intensity;

[0034] Figure 4 Rhodamine 6G at 613 cm -1 The relationship between signal peak intensity and Rhodamine 6G concentration;

[0035] Figure 5 This is a comparison chart of the long-term stability of the carbon-doped silver composite nanoflower SERS substrate and the ordinary silver nanoflower SERS substrate;

[0036] Figure 6 Spectrum of carbon-doped silver composite nanoflower SERS substrate detecting 5ppm crystal violet;

[0037] Figure 7 This is the spectrum of carbon-doped silver composite nanoflower SERS substrate detecting 5ppm methylene blue;

[0038] Figure 8 This is the spectrum of 5ppm malachite green detected on the carbon-doped silver composite nanoflower SERS substrate. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0040] The present invention provides a method for preparing a carbon-doped silver composite nanoflower SERS substrate, comprising the following steps:

[0041] Step 1: grow a nanoflower structure on the surface of an alumina substrate using a vapor phase chemical deposition method.

[0042] The specific method is as follows:

[0043] First, in a 100 mbar low-pressure H2 environment, NH3 and trimethylgallium were introduced to grow a GaN buffer layer on an alumina substrate at 520°C, and annealed at 1040°C for 120 seconds. Then, a 2 μm undoped GaN layer was grown on the GaN buffer layer at 1020°C.

[0044] Next, a 3nm silicon-doped In layer was grown on the undoped GaN layer in a low-pressure N2 environment. x Ga 1-x N, x = 0.15-0.25, forming a rough surface, where the silicon doping content is 1×10 20 / cm 3 ;

[0045] Finally, in a 100 mbar low-pressure N2 environment, NH3 and trimethylgallium were introduced, and unintentionally doped gallium nitride and highly doped gallium nitride were periodically grown at 1020°C. The growth time was 180 seconds for both layers, and the growth was repeated for 5-10 cycles. The highly doped gallium nitride layer maintained a rough surface during growth, while the unintentionally doped gallium nitride layer caused the nanoflower structure to grow rapidly, ultimately forming a large-area uniform gallium nitride nanoflower structure.

[0046] Step 2: The surface of the substrate on which the GaN nanoflower structure is grown is subjected to an amino treatment to form multiple amino sites on the surface of the GaN nanoflower, which is beneficial to the combination of the carbon-doped nanostructure on the surface of the GaN nanoflower.

[0047] The specific method is as follows:

[0048] First, the cleaned substrate was placed with the GaN nanoflower structure facing upward and plasma treated for 10 minutes in an oxygen environment.

[0049] Then, the treated substrate was immersed in an ethanol solution of 3-aminopropyltriethoxysilane with a volume concentration of 5% for 10 hours;

[0050] Finally, the substrate was placed in ultrapure water for cleaning for 30 minutes, taken out and dried with nitrogen for later use, thereby achieving amino treatment on the surface of the substrate.

[0051] Step three, growing carbon-doped silver composite nanoparticles on the surface of the substrate after the amination treatment.

[0052] The specific method is as follows:

[0053] First, add 5 mL of 50 mM silver nitrate solution into a sealable bottle, then add 5 mL of 10 mM hexadecylpyridine solution, observe the color change from colorless to milky white, and stir in a dark environment for 30 min at a controlled speed of 500 rpm;

[0054] Then, the substrate after the amino treatment was placed in a bottle, and then 2 mL of 2M sodium hydroxide solution was added at one time. The color immediately turned brown and then black. After obvious precipitation was seen, it was left to grow in the dark for 12 hours.

[0055] Finally, the substrate was taken out, ultrasonically cleaned with ultrapure water, and dried with nitrogen, and the preparation of the carbon-doped silver composite nanoflower SERS substrate was completed.

[0056] Application performance testing:

[0057] All Raman signal verifications in the present invention are detected using Rhodamine 6G solution: first, Rhodamine 6G solutions of different concentrations are prepared as required, then 2 μL of the prepared Rhodamine 6G solution is added to the prepared carbon-doped silver composite nanoflower SERS substrate, and the Raman mapping spectrum is measured after natural drying.

[0058] All Raman tests require the same control conditions: the power is 0.25-1mW, the wavelength is 532nm, the laser is focused by a 50x telephoto lens and irradiated onto the sample surface, the scanning area is 100 points of 10μm×10μm, the exposure time of each point is 1s, and the central wave number of data collection is 1300cm -1 .

[0059] 1. Surface morphology characterization

[0060] The surface of the prepared carbon-doped silver composite nanoflower SERS substrate was observed by scanning electron microscopy. Figure 1 As shown, it can be seen that carbon-doped silver nanoparticles are evenly distributed on the surface of the GaN nanoflower structure, forming a good SERS substrate.

[0061] 2. Hydrophobic performance test

[0062] In order to verify that the carbon-doped silver composite nanoflower SERS substrate prepared in the present invention has good hydrophobicity, the hydrophobic angle of the substrate was measured. Figure 2 As shown, the results show that the hydrophobic angle is between 125 and 130°, indicating that the substrate has good hydrophobicity.

[0063] 3. Relationship between substrate hydrophobicity and SERS detection sensitivity

[0064] In order to verify that the SERS substrate of the present invention can focus the detection substance to the location of the hot spot and further improve the sensitivity of SERS detection, a relationship between the hydrophobicity of the substrate and the SERS enhancement effect was drawn (using the measurement of 10 -6 M rhodamine 6G solution as an example), the results are shown in Figure 3 As shown, from Figure 3 It can be seen that the better the hydrophobicity of the substrate, the more hot spots are formed by the carbon-doped silver composite nanoparticles on the substrate, the more the analytes can be focused on the hot spot positions, and the higher the sensitivity of substrate SERS detection.

[0065] 4. Relationship between Rhodamine 6G concentration and SERS detection sensitivity

[0066] In order to verify that the SERS substrate of the present invention has a strong SERS detection sensitivity, a curve diagram of the relationship between the intensity of the SERS signal peak and the concentration of rhodamine 6G was drawn, see Figure 4 As shown, 10-12 M, and the enhancement factor of the carbon-doped silver composite nanoflower SERS substrate was calculated to be 2.48×10 9 .

[0067] 5. Stability of carbon-doped silver composite nanoflower SERS substrate

[0068] In order to verify that the carbon-doped silver composite nanoflower SERS substrate of the present invention has better long-term effectiveness than the general silver nanoflower substrate, the long-term stability of carbon-doped silver nanoparticles on gallium nitride nanoflowers was compared and analyzed. Figure 5 By comparison, it was found that compared with the exponential decay of the Raman signal of the ordinary silver nanoflower substrate, the carbon-doped silver composite nanoflower SERS substrate can maintain 90% signal stability within 8 months, indicating that the carbon-doped silver composite nanoparticles have high long-term stability.

[0069] 6. Application of carbon-doped silver composite nanoflower SERS substrate in detecting antibacterial agents

[0070] In order to verify the detection effect of the SERS substrate of the present invention on antibacterial agents, the carbon composite silver nanoflower SERS substrate was used to detect three antibacterial agents, crystal violet, methylene blue and malachite green. First, three solutions of crystal violet, methylene blue and malachite green were prepared with a concentration of 5ppm, and blank samples were prepared. The detection was carried out according to the above R6G detection method. Figure 6-8 As shown, obvious Raman spectra of crystal violet, methylene blue and malachite green can be obtained.

[0071] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a carbon-doped silver composite nanoflower SERS substrate, characterized in that: The substrate comprises a gallium nitride nanoflower structure grown on an alumina substrate, and carbon-doped silver composite nanoparticles grown on the surface of the gallium nitride nanoflower structure; the preparation method comprises the following steps: Step 1, growing a gallium nitride nanoflower structure on the surface of an alumina substrate by using a vapor phase chemical deposition method; Step 2, performing an amino treatment on the surface of the substrate on which the GaN nanoflower structure is grown; Step 3, growing carbon-doped silver composite nanoparticles on the surface of the substrate after the amination treatment; The specific method of step one is as follows: First, in a low-pressure H2 environment, NH3 and trimethylgallium were introduced to grow a GaN buffer layer on an alumina substrate at 500-550°C, and annealed at 1040°C for 120 seconds. Then, a 2 μm undoped GaN layer was grown on the GaN buffer layer at 1000-1040°C. Next, a 3 nm silicon-doped In layer was grown on the undoped GaN layer at 700°C in a low-pressure N2 environment. x Ga 1-x N, x = 0.15-0.25, forming a rough surface, where the silicon doping content is 1×10 20 / cm 3 ; Finally, in a low-pressure N2 environment, NH3 and trimethylgallium were introduced, and unintentionally doped GaN and highly doped GaN were grown periodically at 1000-1040°C, with a growth time of 180 seconds for 5-10 cycles to form a GaN nanoflower structure. The specific method of step 2 is as follows: First, place the cleaned GaN nanoflower structure upward and treat it with plasma for 3-10 minutes in an oxygen environment. Then, the treated substrate was immersed in an ethanol solution of 3-aminopropyltriethoxysilane for 6 to 12 h; Finally, the substrate was washed in ultrapure water for 10-30 min, taken out and dried with nitrogen for later use, thus achieving amino treatment on the substrate surface. The specific method of step three is as follows: First, add 5 mL of 40-50 mM silver nitrate solution into a sealable bottle, then add 5 mL of 10-15 mM hexadecylpyridine solution. After observing the color change from colorless to milky white, stir in a dark environment for 30 min at a speed of 400-500 rpm. Then, put the amination-treated substrate into a bottle, and then add 2 mL of 1-2 M sodium hydroxide solution at one time. The color immediately turns brown and then black. After obvious precipitation is seen, let it grow in the dark for 6-18 hours. Finally, the substrate was taken out, ultrasonically cleaned with ultrapure water, and dried with nitrogen, and the preparation of the carbon-doped silver composite nanoflower SERS substrate was completed.

2. The method for preparing a carbon-doped silver composite nanoflower SERS substrate according to claim 1, characterized in that: In the ethanol solution of 3-aminopropyltriethoxysilane, the volume ratio of 3-aminopropyltriethoxysilane to ethanol is 5:

95.

3. Application of the carbon-doped silver composite nanoflower SERS substrate prepared by the preparation method as claimed in claim 1 in detecting antibacterial agents.

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