A metastable star-shaped gold nanoflower film, a preparation method and application thereof
Patent Information
- Application Number
- CN202610807723.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-05
- Publication Date
- 2026-08-28
AI Technical Summary
但是现有技术中多采用滴加法或金纳米颗粒自组装薄膜作为固体SERS基底，但是其存在以下缺陷：（1）热点密度低：实心金纳米颗粒表面光滑，依赖颗粒之间的间隙产生有限热点，信号弱且不匀；（2）组装不可控：滴加法易产生“咖啡环”效应
[0031] 1. This invention employs sharp, star-shaped gold nanoflowers for self-assembly, resulting in higher hotspot density and increased number of hotspots due to the nano-gap between the spikes, thus significantly improving the Raman signal enhancement effect.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of microfluidic synthesis, nano-self-assembly and surface-enhanced Raman scattering technology, specifically relating to a metastable star-shaped gold nanoflower thin film, its preparation method and application. Background Technology
[0002] Solid SERS substrates have advantages in real-time monitoring due to their ease of handling and recycling. However, existing technologies mostly use drop-addition or gold nanoparticle self-assembled films as solid SERS substrates, but these have the following drawbacks: (1) Low hot spot density: Solid gold nanoparticles have smooth surfaces, and the limited hot spots generated depend on the gaps between particles, resulting in weak and uneven signals; (2) Uncontrollable assembly: Drop-addition is prone to producing the "coffee ring" effect. Traditional spin-coating methods tend to lead to random particle stacking, resulting in poor film uniformity; (3) Uncontrollable morphology: It is difficult to control the tip structure of particles with different sizes. Therefore, it is necessary to develop new solid SERS substrates.
[0003] Current literature reports on the use of organic solvents to induce nanoparticle assembly primarily target spherical particles, and the SERS signals are not high. On one hand, traditional beaker synthesis methods heavily rely on surfactants (such as CTAB and CTAC) or require the preparation of complex core-shell structures as templates. These added organic compounds are difficult to completely remove, leaving some residues on the nanoparticle surface, potentially leading to biotoxicity. Large amounts of surfactants can interfere with the electromagnetic field distribution on the particle surface, affecting its performance in SERS or photothermal conversion, thus hindering its application in the biomedical field. On the other hand, metastable star-shaped or flower-shaped nanostructures are often thermodynamically unstable and prone to ripening during synthesis, gradually evolving into lower-energy spherical structures. Furthermore, uneven local temperature and concentration within the reactor can lead to poor batch-to-batch reproducibility and make continuous, large-scale production difficult.
[0004] Therefore, there is a need for a metastable star-shaped gold nanoflower self-assembled SERS substrate that is suitable for high-sensitivity SERS detection, while also being batch reproducible and having a clean surface. Summary of the Invention
[0005] To address some shortcomings in existing technologies, this invention provides a metastable star-shaped gold nanoflower thin film, its preparation method, and its applications. This invention prepares a metastable star-shaped gold nanoflower thin film based on microfluidic synthesis and interfacial self-assembly. The film is formed by the close packing of star-shaped gold nanoflowers with an average particle size of 54 nm through hexane-ethanol-induced interfacial self-assembly, resulting in a higher hotspot density and increased number of hotspots due to the nano-gap between the spikes, significantly enhancing the Raman signal. The preparation method simplifies the star-shaped gold nanoflower preparation process and facilitates reproducibility. The self-assembly process uses low-toxicity hexane and ethanol, simplifying the assembly steps. The operation is simple, the product variation is small, and no additional surfactant is required, making it highly practical.
[0006] To achieve the above-mentioned technical objectives, the present invention employs the following technical means:
[0007] This invention first provides a method for preparing metastable star-shaped gold nanoflowers, the method comprising:
[0008] (1) Mix hydroxylamine hydrochloride aqueous solution with gold nanoparticle colloidal solution to obtain solution A; add sodium hydroxide to tetrachloroauric acid aqueous solution until the golden yellow color disappears, the solution is clear and transparent and there is no precipitate, adjust the pH value to obtain solution B;
[0009] (2) Liquid A and liquid B are mixed and reacted in a fishbone-shaped chip through a microfluidic system to obtain metastable star-shaped gold nanoflowers.
[0010] Preferably, in step (1), the concentration of the aqueous solution of hydroxylamine hydrochloride in solution A is 0.04M, and the concentration of the colloidal solution of gold nanoparticles is 0.25mM;
[0011] The volume ratio of the hydroxylamine hydrochloride aqueous solution to the gold nanoparticle solution is 1:9;
[0012] The gold nanoparticles have a particle size of 10~60 nm.
[0013] Preferably, in step (1), the particle size of the gold nanoparticles is 20 nm.
[0014] Preferably, in step (1), the concentration of the tetrachloroauric acid aqueous solution in solution B is 0.01~0.1wt%; and the concentration of the sodium hydroxide solution is 1mol / L.
[0015] Adjust the pH value to 11-12.
[0016] Preferably, the concentration of the tetrachloroauric acid aqueous solution is 0.01 wt%.
[0017] Preferably, in step (2), liquid A and liquid B are mixed at a volume ratio of 1:11;
[0018] In the microfluidic system, the flow rate of liquid A is 0.5~1 mL / min, and the flow rate ratio of liquid A to liquid B is 1~2:11;
[0019] The reaction temperature is 15~30℃.
[0020] The present invention also provides metastable star-shaped gold nanoflowers prepared by the above preparation method, wherein the surface of the metastable star-shaped gold nanoflowers has obvious rough protrusion structure; the average particle size is 50-210 nm.
[0021] The present invention also provides a method for preparing a metastable star-shaped gold nanoflower film, the method comprising: tightly stacking star-shaped gold nanoflowers through interfacial self-assembly induced by hexane-ethanol to form a metastable star-shaped gold nanoflower film.
[0022] Preferably, the preparation method includes:
[0023] Centrifuge the metastable star-shaped gold nanoflower solution, discard the supernatant, and then resuspend it in deionized water to obtain a star-shaped gold nanoflower colloidal solution.
[0024] A mixed solution of hexane and ethanol was added dropwise to a colloidal solution of star-shaped gold nanoflowers. After observing the formation of a thin film, the film was bonded to a silicon wafer and allowed to stand to evaporate, thus obtaining the metastable star-shaped gold nanoflower thin film.
[0025] Preferably, the volume ratio of hexane to ethanol in the mixed solution of hexane and ethanol is 4:1;
[0026] The concentration of the star-shaped gold nanoflora colloidal solution was 20 μmol / L;
[0027] The volume ratio of the colloidal solution of star-shaped gold nanoflowers to the mixed solution of n-hexane and ethanol is 2:1.
[0028] The present invention also provides a metastable star-shaped gold nanoflower thin film prepared by the above method.
[0029] The present invention also provides the application of the above-mentioned metastable star-shaped gold nanoflowers, or the above-mentioned metastable star-shaped gold nanoflower films, in SERS detection.
[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0031] 1. This invention employs sharp, star-shaped gold nanoflowers for self-assembly, resulting in higher hotspot density and increased number of hotspots due to the nano-gap between the spikes, thus significantly improving the Raman signal enhancement effect.
[0032] 2. The metastable star-shaped gold nanoflower film of the present invention has good uniformity, and the interface self-assembles to form a large-area ordered structure with RSD<15%.
[0033] 3. The SERS substrate prepared by the metastable star-shaped gold nanoflower film of the present invention has high sensitivity, with a detection limit of 10⁻¹³ mol / L for 4-MBA, which is 1000 times higher than that of solid particle film.
[0034] 4. The process for preparing star-shaped gold nanoflowers in this invention is simplified and easy to repeat. The self-assembly process uses low-toxicity n-hexane and ethanol, which simplifies the assembly steps. Attached Figure Description
[0035] Figure 1 This is a macroscopic image showing the self-assembly of gold nanoflower thin films.
[0036] Figure 2 This is an image of a self-assembled gold nanoflower film observed under an optical microscope.
[0037] Figure 3 SEM comparison images of star-shaped gold nanoflowers (left) and solid gold nanoparticles (right).
[0038] Figure 4 Scanning electron microscope (SEM) images of star-shaped gold nanoflowers with different particle sizes; the left image shows an average particle size of 140 nm, and the right image shows an average particle size of 210 nm.
[0039] Figure 5 This is a SEM image of the surface morphology of a solid gold nanoparticle film.
[0040] Figure 6 SEM images of the surface morphology of the star-shaped gold nanoflower film (a. low magnification; b. high magnification).
[0041] Figure 7 Zeta potential diagram of gold nanoflowers before and after 4-MBA connection.
[0042] Figure 8 Two thin films for 4-MBA (10⁻) 6 Comparison of SERS spectra of M).
[0043] Figure 9 The SERS spectra of gold nanoflower films and gold nanoparticle films are shown in the figure; a in the figure is the SERS spectrum of the gold nanoflower film enhancing the 4-MBA Raman signal at 1×10⁻ 6 ~10 -13 Sensitivity test of M, b is the sensitivity test of Figure a at 1×10 -11 ~10 -13 M represents supplementary low-concentration spectral data, and c represents the enhancement of the 4-MBA Raman signal by gold nanoparticle film at 1×10⁻⁻⁻⁴ ...�⁻⁴⁴⁴⁴⁴⁴⁴⁴⁴⁴⁴ 6 ~10 -10 Sensitivity test of M
[0044] Figure 10Different sites on gold nanoflower thin films for 4-MBA (10⁻) 6 M) SERS spectrum of repeated sampling. Detailed Implementation
[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.
[0046] Example 1:
[0047] 200 μL of 0.04 mol / L hydroxylamine hydrochloride aqueous solution was mixed with 1.8 mL of 0.25 mM 20 nm gold nanoparticle colloidal solution to obtain 2 mL of solution A; 21.98 mL of 0.25 mM tetrachloroauric acid aqueous solution was titrated with 1 mol / L sodium hydroxide until the golden color disappeared (approximately 24 μL was required), the solution was clear and transparent without precipitation, and the pH was adjusted to about 11.2 to obtain 22 mL of solution B;
[0048] Solution A and solution B were mixed and reacted in a fishbone-shaped chip using a microfluidic system at flow rates of 0.5 mL / min and 5.5 mL / min, respectively. The mixture was collected from the outlet using a vial or a 50 mL centrifuge tube to obtain metastable star-shaped gold nanoflowers with an average particle size of 54 nm.
[0049] (2) Preparation of metastable star-shaped gold nanoflower thin films:
[0050] Take 10 mL of the metastable star-shaped gold nanoflowers obtained in step (1) and centrifuge at 4℃ for 5 min at 7000 rpm. Discard the supernatant and resuspend in 2 mL of deionized water to obtain a metastable star-shaped gold nanoflower colloidal solution.
[0051] Hexane and ethanol were mixed in a volume ratio of 4:1, and 1 mL was added dropwise to a resuspended metastable star-shaped gold nanoflower colloidal solution. After the film formation was observed, the film was retrieved from bottom to top using a plasma-cleaned silicon wafer or a silanized glass slide, either manually or mechanically, so that the gold nanoflower film was bonded to the silicon wafer. The film was allowed to stand for 1 min to evaporate, and the metastable star-shaped gold nanoflower film was obtained.
[0052] Figure 1 This is a macroscopic image of the self-assembly of gold nanoflower thin films. As can be seen from the image, the films are loaded relatively flat and uniformly on the glass slide, and the films exhibit the natural color of gold.
[0053] Figure 2 The image shows the self-assembled gold nanoflower film under an optical microscope. As can be seen from the image, the gold nanoflower film is relatively uniformly distributed, without prominent overlap or haloing, thus avoiding the coffee ring effect.
[0054] Figure 3 The image shows a SEM comparison of star-shaped gold nanoflowers (left) and solid gold nanoparticles (right). It can be seen from the image that, for the same particle size, gold nanoflowers have a rougher surface morphology, while solid gold nanoparticles have a smoother surface morphology.
[0055] Figure 4 The images show scanning electron microscope (SEM) images of star-shaped gold nanoflowers with different particle sizes. The left image shows an average particle size of 140 nm, and the right image shows an average particle size of 210 nm. As can be seen from the images, the star-shaped structure becomes more prominent and obvious with increasing particle size.
[0056] Figure 5 The image shows the SEM surface morphology of the solid gold nanoparticle film. As can be seen from the image, the gold nanoparticles have a relatively uniform particle size and similar dimensions, and no other morphological structures are observed.
[0057] Figure 6 The images show the SEM surface morphology of the star-shaped gold nanoflower film (a. low magnification; b. high magnification). As can be seen from the images, the star-shaped gold nanoflowers are relatively uniformly distributed. At low magnification, fewer cavities are observed, but the overall density is high. At high magnification, the gold nanoflowers are densely packed with small gaps, theoretically providing more SERS "hot spots."
[0058] Example 2:
[0059] (1) Preparation of metastable star-shaped gold nanoflowers with a particle size of 140 nm:
[0060] 200 μL of 0.4 mol / L hydroxylamine hydrochloride aqueous solution was mixed with 1.8 mL of 0.25 mM 35 nm gold nanoparticle colloidal solution to obtain 2 mL of solution A; 21.9 mL of 1.3 mM tetrachloroauric acid aqueous solution was titrated with 1 mol / L sodium hydroxide until the golden color disappeared (approximately 114 μL was required), the solution was clear and transparent without precipitation, and the pH was adjusted to about 11.2 to obtain 22 mL of solution B;
[0061] Solution A and solution B were mixed and reacted in a fishbone-shaped chip using a microfluidic system at flow rates of 0.5 mL / min and 5.5 mL / min, respectively. The mixture was collected from the outlet using a vial or a 50 mL centrifuge tube to obtain metastable star-shaped gold nanoflowers with an average particle size of 140 nm.
[0062] (2) Preparation of metastable star-shaped gold nanoflower thin films:
[0063] Take 10 mL of the metastable star-shaped gold nanoflowers obtained in step (1) and centrifuge at 4℃ for 5 min at 7000 rpm. Discard the supernatant and resuspend in 2 mL of deionized water to obtain a metastable star-shaped gold nanoflower colloidal solution.
[0064] Hexane and ethanol were mixed in a volume ratio of 4:1, and 1 mL was added dropwise to a resuspended metastable star-shaped gold nanoflower colloidal solution. After the film formation was observed, the film was retrieved from bottom to top using a plasma-cleaned silicon wafer or a silanized glass slide, either manually or mechanically, so that the gold nanoflower film was bonded to the silicon wafer. The film was allowed to stand for 1 min to evaporate, and the metastable star-shaped gold nanoflower film was obtained.
[0065] (3) Connection of 4-MBA probes:
[0066] Take the gold nanoflowers with an average size of 140 nm obtained in (1), centrifuge at 7000 rpm for 5 min at 4℃, discard the supernatant, add 2 mL of deionized water to resuspend, and obtain a metastable star-shaped gold nanoflower colloidal solution. Divide it into two equal portions and label them as solution a and solution b.
[0067] Add 1 μL of the prepared solution with a concentration of 1×10 to solution b. -3 The final concentration of 4-MBA in the ethanol stock solution of 4-MBA probe (mol / L) after thorough mixing is 1×10⁻⁶. -6 mol / L. After incubation for 30 min, centrifuge at 7000 rpm for 5 min at 4℃, discard the supernatant, add 2 mL of deionized water to resuspend, and obtain the treated solution b, which will be used for subsequent tests.
[0068] The obtained solution a and the treated solution b were subjected to Zeta potential testing. After connecting a 4-MBA probe, the potential of the gold nanoflower decreased from -8.8±0.2 mV to -21.1±0.6 mV. Figure 7 ).
[0069] Example 3:
[0070] (1) Preparation of metastable star-shaped gold nanoflowers with a particle size of 210 nm:
[0071] Solution A was prepared by mixing 420 μL of 0.12 mol / L hydroxylamine hydrochloride aqueous solution with 1.58 mL of 0.02 mM 60 nm gold nanoparticle solution. Solution B was prepared by titrating 21.9 mL of 0.755 mM tetrachloroauric acid aqueous solution with 1 mol / L sodium hydroxide until the gold color disappeared (approximately 66 μL was required). The solution was clear and transparent without precipitate. The pH was adjusted to approximately 11.2 to obtain solution B.
[0072] Solution A and solution B were mixed and reacted in a fishbone-shaped chip using a microfluidic system at flow rates of 0.5 mL / min and 5.5 mL / min, respectively. The mixture was collected from the outlet using a vial or a 50 mL centrifuge tube to obtain metastable star-shaped gold nanoflowers with an average particle size of 210 nm.
[0073] (2) Preparation of metastable star-shaped gold nanoflower thin films:
[0074] Take 10 mL of the metastable star-shaped gold nanoflowers obtained in step (1) and centrifuge at 4℃ for 5 min at 7000 rpm. Discard the supernatant and resuspend in 2 mL of deionized water to obtain a metastable star-shaped gold nanoflower colloidal solution.
[0075] Hexane and ethanol were mixed in a volume ratio of 4:1, and 1 mL was added dropwise to a resuspended metastable star-shaped gold nanoflower colloidal solution. After the film formation was observed, the film was retrieved from bottom to top using a plasma-cleaned silicon wafer or a silanized glass slide, either manually or mechanically, so that the gold nanoflower film was bonded to the silicon wafer. The film was allowed to stand for 1 min to evaporate, and the metastable star-shaped gold nanoflower film was obtained.
[0076] Example 4:
[0077] In this embodiment, the Raman spectral enhancement effect of the metastable star-shaped gold nanoflower film of the present invention was investigated using the self-assembled gold nanoparticle film as a control. The specific steps are as follows: (1) Preparation of the self-assembled gold nanoparticle film:
[0078] Take 10 mL of 0.02 mM 60 nm gold nanoparticles and centrifuge at 4 °C for 5 min at 7000 rpm. Discard the supernatant and resuspend in 10 mL of deionized water to obtain a colloidal solution of gold nanoparticles.
[0079] Hexane and ethanol were mixed in a volume ratio of 4:1, and 3 ml was added dropwise to the resuspended gold nanoparticle colloidal solution. After the film was observed to form, the film was retrieved from bottom to top using a silicon wafer or a clean glass slide that had been cleaned with Plasma, either manually or mechanically, so that the gold nanoflower film was bonded to the silicon wafer. The film was allowed to stand for 1 minute to evaporate, and the gold nanoparticle film was obtained.
[0080] (2) Connection of 4-MBA probes:
[0081] Prepare 20 ml of solution with a concentration of 1×10 using the stepwise dilution method. -6 Take 10 ml of mol / L 4-MBA solution and treat the gold nanoparticle self-assembled film and the gold nanostar self-assembled film for 30 min. After treatment, slowly rinse away the excess probe with anhydrous ethanol.
[0082] (3) Raman spectroscopy enhancement effect test
[0083] A 633nm laser with an intensity of 30mW and a collection time of 5s was used to test the Raman spectral signal enhancement effect on the self-assembled gold nanoparticle film and the metastable star-shaped gold nanoflower film described in Example 1. Three signal acquisitions were performed, and the test results are as follows: Figure 8 As shown in the figure, under the same conditions, the enhancement effect of the gold nanoflower self-assembled film is better than that of the gold nanoparticle self-assembled film.
[0084] Example 5:
[0085] This embodiment uses a gold nanoparticle self-assembled film as a control to examine the sensitivity of the metastable star-shaped gold nanoflower film described in this invention. The specific steps are as follows:
[0086] Multiple gold nanoflower films and gold nanoparticle films were prepared according to the steps described in Examples 4 and 1 for later use.
[0087] Prepare a concentration of 1×10 using the stepwise dilution method. -6 ~1×10 -13 Prepare 20 mL of 4-MBA solution at mol / L for each sample. Take 10 mL of each solution and treat the gold nanoparticle self-assembled membrane and the gold nanostar self-assembled membrane for 30 min. After treatment, slowly rinse away the excess probe with anhydrous ethanol.
[0088] A 633nm laser with an intensity of 30mW was used, and the acquisition time was 5s to test the Raman spectroscopy signal enhancement effect. Three signal acquisitions were performed. (The last sentence appears to be incomplete and possibly refers to a 1×10⁻⁶ laser.) -6 The mol / L group was randomly sampled at selected locations and the result was obtained by integration at 1078 cm⁻¹. -1 Calculate the peak area at the specified location and then calculate the RSD.
[0089] Test results are as follows Figure 9 and Figure 10 As shown, from Figure 9 As can be seen, the gold nanoflower self-assembled film exhibits better Raman signal enhancement. Comparison shows that under the aforementioned detection conditions, the SERS detection sensitivity of the gold nanoflower self-assembled film is higher than that of the gold nanoparticle self-assembled film. Figure 10 It can be seen that the gold nanoflower self-assembled film is relatively uniformly distributed, with a relatively stable enhancement effect, RSD<15%, and has good repeatability.
[0090] Therefore, gold nanoflowers prepared by microfluidic control exhibit good Raman signal enhancement after self-assembly into films, and the experiments are highly reproducible.
[0091] In summary, this invention prepares metastable star-shaped gold nanoflower films based on microfluidic synthesis and interfacial self-assembly. These films are formed by the close packing of star-shaped gold nanoflowers with an average particle size of 54 nm through hexane-ethanol-induced interfacial self-assembly, resulting in a higher hotspot density and increased number of hotspots due to the nano-gap between the spikes, thus significantly enhancing the Raman signal. The preparation method is simplified and reproducible, and the use of low-toxicity hexane and ethanol in the self-assembly process simplifies the assembly steps. The process is easy to operate, produces products with minimal variation, and requires no additional surfactants, demonstrating excellent practicality.
[0092] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. A method for preparing metastable star-shaped gold nanoflowers, characterized in that, The preparation method includes: (1) Mix hydroxylamine hydrochloride aqueous solution with gold nanoparticle colloidal solution to obtain solution A; add sodium hydroxide to tetrachloroauric acid aqueous solution until the golden yellow color disappears, the solution is clear and transparent and there is no precipitate, adjust the pH value to obtain solution B; (2) Liquid A and liquid B are mixed and reacted in a fishbone-shaped chip through a microfluidic system to obtain metastable star-shaped gold nanoflowers.
2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of hydroxylamine hydrochloride aqueous solution in solution A is 0.04M, and the concentration of gold nanoparticle colloidal solution is 0.25mM; The volume ratio of the hydroxylamine hydrochloride aqueous solution to the gold nanoparticle solution is 1:9; The gold nanoparticles have a particle size of 10~60 nm.
3. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the tetrachloroauric acid aqueous solution in solution B is 0.01~0.1wt%; the concentration of the sodium hydroxide solution is 1mol / L. Adjust the pH value to 11-12.
4. The preparation method according to claim 1, characterized in that, In step (2), liquid A and liquid B are mixed at a volume ratio of 1:11; In the microfluidic system, the flow rate of liquid A is 0.5~1 mL / min, and the flow rate ratio of liquid A to liquid B is 1~2:11; The reaction temperature is 15~30℃.
5. The metastable star-shaped gold nanoflowers prepared by the preparation method according to any one of claims 1-4, characterized in that, The surface of the metastable star-shaped gold nanoflowers has a distinct rough, protruding structure. Average particle size 50-210 nm.
6. A method for preparing a metastable star-shaped gold nanoflower thin film, characterized in that, The preparation method includes: tightly stacking the star-shaped gold nanoflowers described in claim 5 through interfacial self-assembly induced by hexane-ethanol to form a metastable star-shaped gold nanoflower film.
7. The preparation method according to claim 6, characterized in that, The preparation method includes: Centrifuge the metastable star-shaped gold nanoflower solution, discard the supernatant, and then resuspend it in deionized water to obtain a star-shaped gold nanoflower colloidal solution. A mixed solution of hexane and ethanol was added dropwise to a colloidal solution of star-shaped gold nanoflowers. After observing the formation of a thin film, the film was bonded to a silicon wafer and allowed to stand to evaporate, thus obtaining the metastable star-shaped gold nanoflower thin film.
8. The preparation method according to claim 7, characterized in that, In a mixed solution of n-hexane and ethanol, the volume ratio of n-hexane to ethanol is 4:
1. The concentration of the star-shaped gold nanoflora colloidal solution was 20 μmol / L; The volume ratio of the colloidal solution of star-shaped gold nanoflowers to the mixed solution of n-hexane and ethanol is 2:
1.
9. The metastable star-shaped gold nanoflower thin film prepared according to any one of claims 6-8.
10. The application of the metastable star-shaped gold nanoflowers of claim 5 or the metastable star-shaped gold nanoflower thin film of claim 9 in SERS detection.