SERS (Surface Enhanced Raman Scattering) detection method for constructing hot-spot ordered multilayer nano array based on temperature-driven shrinkage liquid drops

Abstract

The invention discloses an SERS (Surface Enhanced Raman Scattering) detection method for constructing a hot-spot ordered multilayer nano array based on temperature-driven shrinkage liquid drops, which comprises the following steps of: changing the surface tension of a gas-liquid interface by utilizing temperature change to generate a thermal capillary effect or a Malangori effect, and regulating and controlling the dynamic shrinkage process of the nano sol liquid drops; the target molecules are actively transported into the uniformly distributed hot spot ordered multi-layer nano array structure, coffee rings caused by the reduction of the uniformity of the nano array are avoided, and then a target object signal is detected under a Raman spectrometer. Circulating convection is generated through the synergistic effect of the Malangori effect and the coffee ring effect, and the nano particles in the contracted liquid drops can circularly flow in the centers and the edges of the liquid drops. Therefore, an ordered multi-layer nano array with uniformly distributed hot spots can be constructed in a liquid drop shrinkage process, and meanwhile, high-sensitivity and high-stability detection of SERS of target molecules in the hot spots can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of Raman spectroscopy, and particularly relates to a SERS detection method based on temperature-driven shrinkage of liquid droplets to construct hot spot ordered multilayer nano array. BACKGROUND

[0002] The signal stability and sensitivity of surface-enhanced Raman spectroscopy (SERS) is the core problem and technical difficulty in the current scientific community. Developing SERS substrates with high enhancement effect has become the core research direction in this field. As early as 1974, it was found that the signal of molecules can be greatly enhanced on a rough silver electrode. Then in 1977, the concept of "surface-enhanced Raman scattering" was defined and explained. Up to now, the enhancement mechanism of surface-enhanced Raman scattering has been more deeply understood, especially the Raman scattering characteristics of SERS hot spots, which are usually pointed to the cracks and micro gap structures protruding from the surface of the substrate, and they are the core active sites for achieving high-efficiency enhancement of Raman signals. All these researches aim to design nanoparticles with different morphologies to achieve better SERS enhancement effect.

[0003] In the solid nano array method, uniform nanoscale hot spots are prepared by different end-capping agents, block copolymer self-assembly or convection self-assembly technology. The analyte liquid on the solid nano array substrate may not be uniformly adsorbed during the drying process due to the coffee ring effect (i.e. the evaporation rate of solvent at the edge of the droplet is faster than that at the center, resulting in the migration and enrichment of solute to the edge), and the number of effective hot spots is small, resulting in a decrease in signal uniformity.

[0004] Constructing nano hot spots with uniform structure and effectively positioning analyte molecules to plasmonic hot spot regions are the core research objectives in the field of SERS analysis technology, and are also the key direction to improve the performance of SERS detection. SUMMARY

[0005] Based on the problems in the background art, the present application provides a SERS detection method based on temperature-driven shrinkage of liquid droplets to construct hot spot ordered multilayer nano array, which has simple steps and can realize the sensitivity and stability of surface-enhanced Raman spectroscopy detection. The method of the present application is also beneficial to realize the wide application of surface-enhanced Raman spectroscopy detection to target objects.

[0006] To solve the above problems, the technical scheme adopted by the present application is: The SERS detection method of constructing hot spot ordered multilayer nano array based on temperature-driven shrinking liquid drops uses temperature change to change the surface tension of gas-liquid interface to produce thermal capillary effect or Marangoni effect, to regulate the dynamic process of nano sol liquid drop shrinking, to make target molecules actively transport into the ordered multilayer nano array structure of hot spots, to avoid the coffee ring caused by the decrease of nano array uniformity, and then to detect the target signal under the Raman spectrometer.

[0007] The ordered multilayer nano array is formed by the convection self-driven deposition of nanoparticles on the substrate to form a nanoscale hot spot. Generally, the following scheme can be used: Preparation of super-hydrophobic zinc oxide nano substrate; centrifugal collection of metal nano sol to concentrate the bottom nano sol; dispersion of the concentrated nano sol into water to form a nano particle sol; formation of a shrinking liquid drop on the super-hydrophobic zinc oxide nano substrate by taking the nano particle sol and the target molecule, and formation of an ordered multilayer nano array under temperature driving. The metal nano sol includes but is not limited to silver nano sol, gold nano sol, copper nano sol, nickel nano sol, and palladium nano sol. The metal nano sol can be commercially available products such as products of Xianfeng Nanometer Company, etc., or can be prepared by the conventional sodium citrate method.

[0008] Further, the diameter of the nanoparticles used to form the ordered multilayer nano array is 50-100 nm, and after centrifugation, the concentration of the colloidal solution is about 1.0×10 10 particles / μL, and the volume dilution ratio of 1:2 is preferred. The morphology of the ordered multilayer nano array includes but is not limited to nanospheres, nanorods, nanowires, and nanopolyhedra, etc.

[0009] Further, the substrate material includes but is not limited to silicon wafer, mica sheet, glass sheet, quartz, etc., and the surface of the flat material suitable for loading nanoparticles should not have obvious Raman peaks to affect the subsequent Raman detection. The thickness of the flat material is preferably 100-500 μm.

[0010] Further, the zinc oxide on the super-hydrophobic nano substrate is grown by hydrothermal reaction, which is mostly in the form of nanoflower structure with a diameter of about 200 nm and a length of 1-2 μm, and irregularly stacked with a large number of pores between them.

[0011] Further, the concentrated nano particle sol and the target molecule are formed into a shrinking liquid drop on the super-hydrophobic zinc oxide nano substrate, and under the temperature driving of 30-50℃, the temperature and the concentration of the nanoparticles are regulated to form an ordered multilayer nano array.

[0012] Further, in the dynamic process of shrinking the droplet, circulating convection is generated by the synergistic effect of the Marangoni effect and the coffee ring effect, and the nanoparticles in the shrinking droplet can circulate in the center and edge of the droplet. Thus, an ordered multilayer nanoarray with uniform distribution of hot spots can be constructed in the process of droplet shrinkage, and then the signal of the target object under specific temperature conditions can be detected under a Raman spectrometer.

[0013] Further, the target molecules are mainly adsorbed molecules, including but not limited to plasticizers, organic pollutants, antitumor drugs, poisons, toxins, pesticide residues, dyes, antibiotics, explosives and amino acids, etc., and the solution can be an aqueous solution or an organic solution. Specifically, the target objects include but are not limited to methylene blue (mb), rhodamine 6g (r6g), bright green (bg), malachite green (mg), crystal violet (cv), nile blue (nb), and harmful chemicals in daily life such as sudan iii, phen, paba, 4-mba, etc.

[0014] Further, the signal of the target object is detected under a Raman spectrometer, and the excitation light wavelength of the Raman spectrometer can be 532 nm, 633 nm or 785 nm. Further, the Raman spectrometer used can be a large Raman spectrometer in a laboratory, or a portable or handheld Raman spectrometer.

[0015] The present application provides a method for constructing an ordered multilayer nanoarray of uniform nanohot spots, and controlling or guiding the effective positioning of target molecules to the plasmonic hotspot region to realize the sensitivity of surface-enhanced Raman spectroscopy detection. Obviously, the method is not limited to the category of target molecules known to those skilled in the art, and any method based on the mechanism of the present application and capable of realizing the sensitivity of surface-enhanced Raman spectroscopy detection should be included in the protection scope of the present application.

[0016] Working principle: In the constructed hotspot ordered multilayer nanoarray, the diameter of the nanoparticles is 50-100 nm, and the concentration is about 3.3×10 9Particles / μL. When the constructed contracted droplets act on the target molecules, the droplet edges experience rapid evaporation relative to the droplet interior due to the "pinning effect," inducing the solution to carry the solute from the center to the edge. This coffee ring effect leads to rapid evaporation at the contact line of the solution. Driven by temperature, the surface tension at the contact line decreases, causing the solute to flow back from the low surface tension location to the high surface tension center. This forms Marangoni convection from the lower temperature to the higher temperature location. Through the synergistic effect of the Marangoni and coffee ring effects, cyclic convection is generated, allowing nanoparticles in the contracted droplets to circulate between the center and edge of the droplet. Thus, an ordered multilayer nanoarray with uniformly distributed hotspots can be constructed during droplet contraction, enabling highly sensitive and stable SERS detection of target molecules within these hotspots.

[0017] The beneficial effects of this invention are as follows: 1. A concept was proposed to construct shrinking droplet hotspots between ordered multilayer nanoarrays using temperature-driven methods. Through convection-driven autonomous deposition, nanoparticles were directionally deposited onto a superhydrophobic zinc oxide nanosubstrate, forming a uniform nanoscale hotspot structure. The nanoparticles had diameters of 50-100 nm and a concentration of approximately 3.3 × 10⁻⁶. 9 particles / μL, temperature driven at 40℃.

[0018] 2. Utilizing the synergistic effect of the Marangoni and coffee ring effects to generate cyclic convection, analyte molecules are effectively localized to the plasma hotspot region within a uniform hotspot structure formed by an ordered multilayer nanoarray. Furthermore, continuous detection can be performed during the diffusion of the target analyte solution, achieving both sensitivity and stability in surface-enhanced Raman spectroscopy.

[0019] 3. This SERS detection method, based on temperature-driven shrinking droplets constructing hotspot-ordered multilayer nanoarrays, is simple, efficient, and scientifically sound in its preparation. It demonstrates excellent application results for different types of molecules and in various scenarios, making it a universally applicable (widely applicable) surface-enhanced Raman detection method. Attached Figure Description

[0020] Figure 1 This is an optical photograph of a superhydrophobic zinc oxide nanosubstrate. The substrate is uniformly light gray to grayish-white, with no obvious macroscopic color differences or impurity spots on the surface. It exhibits good overall flatness, with no visible cracks, scratches, or protrusions. The film coverage is uniform and dense, without localized peeling or agglomeration, and the zinc oxide coating demonstrates good adhesion to the silicon wafer substrate.

[0021] Figure 2These are scanning images of superhydrophobic zinc oxide nanosubstrates. They mostly exhibit nanoflower-like structures with a diameter of approximately 200 nm and a length of 1–2 μm. These structures are randomly stacked and contain numerous pores, which ensure increased roughness and the achievement of superhydrophobicity.

[0022] Figure 3 This is an optical image of the water contact angle fitted using ImageJ software. In the left image, the deionized water droplet on the substrate surface is a regular spherical or near-spherical shape with a clear and smooth droplet outline, showing no obvious signs of spreading or wetting. The contact area between the droplet and the substrate is extremely small, and the three-phase line (gas-liquid-solid interface) is narrow and clearly defined, visually demonstrating the extremely low adhesion of the substrate to water. The three fitted results of the water contact angle are 162.1°, 151.4°, 157.6°, and 157.0°, respectively. The average water contact angle of 157.0° is taken as the fitted result. Considering the characteristics of superhydrophobic materials, the static contact angle of the water droplet on this substrate surface is ≥150°, and the roll-off angle is ≤10°, which conforms to the typical wettability characteristics of superhydrophobic surfaces.

[0023] Figure 4 Scanning images of silver nanoparticles used to construct this ordered multilayer nanoarray at different magnifications. The nanoparticles have a diameter of 50-100 nm, and after centrifugation, the concentration of the colloidal solution is approximately 1.0 × 10⁻⁶. 10 The particles per μL are relatively uniform in size and exhibit good monodispersity.

[0024] Figure 5 The image shows the UV absorption spectrum of the silver nanoparticles. A significant symmetrical absorption peak appears at 411 nm, which is the surface plasmon resonance (SPR) peak of the spherical silver nanoparticles, indicating that the nanoparticles are predominantly spherical and have good monodispersity. The peak shape shows no obvious shoulders or broadening, indicating uniform particle dispersion and the absence of significant agglomeration or non-spherical morphologies (such as nanorods or nanosheets). The absorbance reaches its maximum at 411 nm and then gradually decreases with increasing wavelength, consistent with the typical SPR spectral behavior of spherical silver nanoparticles.

[0025] Figure 6 The constructed ordered multilayer nanoarray was driven at 40℃ and diluted at a 1:2 volume ratio (3.3 × 10⁻⁶). 9 By shrinking droplets (particles / μL) and detecting SERS spectra on a solution containing the target molecule crystal violet (CV), the 10particles / μL of crystal violet molecules can be achieved. -10 Effective detection at the M level. In the figure, 200 is the intensity scale, and the four spectral lines from top to bottom correspond to 10. -7 M, 10 -8 M, 10 -9 M, 10 -10 M. 1616cm-1 The strong peaks nearby correspond to the stretching vibration of the C=C skeleton of the benzene ring, which is a characteristic Raman vibration mode of the aromatic conjugated structure of crystal violet, directly reflecting the vibrational characteristics of its molecular skeleton.

[0026] Figure 7 To detect the SERS spectrum of the constructed ordered multilayer nanoarray in naturally dried, 1:2 volume ratio shrinking droplets on a solution containing the target molecule crystal violet (CV), the method was achieved. -9 Effective detection at the M level. In the figure, 200 is the intensity scale, and the three spectral lines from top to bottom correspond to 10. -7 M, 10 -8 M, 10 -9 M.

[0027] Figure 8 To test the shrinkage of silver nanoparticle sol in an ordered multilayer nanoarray at a 1:2 volume ratio, under natural drying conditions and at different temperatures, the effect of droplet shrinkage was investigated. -7 Comparison of SERS signals of CV solutions of M. This experiment was conducted at room temperature (20.5 °C) and relative humidity (RH) of 45%. Optimal conditions were a temperature-driven 40 °C and a 10... -7 The SERS signal of the CV solution of M showed a good response to this temperature-driven condition.

[0028] Figure 9 To construct an ordered multilayer nanoarray, the shrinkage of droplets of silver nanoparticles with different concentrations was driven at 40℃. -7 Comparison of SERS signals of CV solutions of M. Silver nanosol particles were diluted at volume ratios of 1:1, 2:3, 1:2, 2:5, and 1:3, with a particle concentration of approximately 5.0 × 10⁻⁶. 9 4.0×10 9 3.3×10 9 2.9×10 9 2.5×10 9 particles / μL. The optimal volumetric dilution ratio is 1:2, 10 -7 The SERS signal of the CV solution of M showed a good response to the volume concentration.

[0029] Figure 10 This invention provides a SERS detection method for constructing hotspot-ordered multilayer nanoarrays using temperature-driven shrinking droplets. Under optimal volume dilution ratio of 1:2 and optimal temperature-driven conditions of 40 °C, the shrinking droplets... -7 The SERS signal change process of CV solution M. The acquisition time was 22 min, and the signal was observed at 1170 cm⁻¹. -1At this location, the relative standard deviation of SERS intensity within a dynamic detection window of 4-9 minutes was 6.04%, demonstrating high repeatability and laying the foundation for quantitative detection.

[0030] Figure 11 This describes the SERS signal variation process under optimal conditions using the method of this invention. The acquisition time was 22 minutes, and the signal was observed at 1616 cm⁻¹. -1 At the location, the relative standard deviation of SERS intensity within the dynamic detection window of 4-9 minutes was 6.77%, demonstrating high repeatability and laying the foundation for quantitative detection.

[0031] Figure 12 A SERS detection method for constructing hotspot-ordered multilayer nanoarrays of naturally dried shrinking droplets was developed, under the same experimental conditions, for 10... -7 SERS signal changes in CV solution M. The acquisition time was 122 min, and the signal was observed at 1170 cm⁻¹. -1 and 1616cm -1 The repeatability at this point is poor.

[0032] Figure 13 A comparison of the contact angle changes of shrinking droplets was made between the SERS detection method for naturally dried shrinking droplets constructing hot-spot ordered multilayer nanoarrays and the SERS detection method for temperature-driven shrinking droplets constructing hot-spot ordered multilayer nanoarrays of the present invention. The contact angle of naturally dried shrinking droplets decreased monotonically; the contact angle fluctuation of temperature-driven shrinking droplets decreased. Under temperature-driven conditions, the droplets undergo a "partial pinning-unpinning" cycle during evaporation. Initially, the droplets exhibit a Cassie state in their microstructure. Evaporation causes the droplets to seep downwards, resulting in a brief increase in the contact angle. Subsequently, as the droplets continue to evaporate, the contact angle decreases again, exhibiting an overall fluctuating trend.

[0033] Figure 14 The images are optical side views taken by a high-speed camera of a 1:2 volume ratio shrinking droplet that has been naturally dried at room temperature. The acquisition time was 133 minutes, with a time interval of 7 minutes.

[0034] Figure 15 The images are optical top-view images taken by a high-speed camera of a 1:2 volume ratio shrinking droplet that has been naturally dried at room temperature. The acquisition time was 133 minutes, with 7-minute intervals.

[0035] Figure 16 The images show SEM images of 1:2 volume-ratio shrinking droplets that have been naturally dried at room temperature. Figures d, e, and f show SEM images at three random locations on the diagonal of Figure b.

[0036] Figure 17This image shows an optical side view of a 1:2 volume-ratio shrinking droplet, driven by the method of this invention at 30°C. The acquisition time was 28.5 min, with a time interval of 1.5 min.

[0037] Figure 18 This is an optical top-view image of a 1:2 volume ratio droplet shrinking using a high-speed camera driven at 30°C according to the method of this invention. The acquisition time was 28.5 min, with a time interval of 1.5 min.

[0038] Figure 19 This is a SEM image of a 1:2 volume ratio shrinking droplet driven by heating at 30°C using the method of the present invention.

[0039] Figure 20 This image shows an optical side view of a 1:2 volume ratio droplet shrinking under 40°C temperature-driven conditions using a high-speed camera. The acquisition time was 19 minutes, with 1-minute time intervals.

[0040] Figure 21 This is an optical top-view image of a 1:2 volume ratio shrinking droplet driven by a high-speed camera using the method of this invention at 40°C. The acquisition time was 19 minutes, with 1-minute time intervals.

[0041] Figure 22 This is a SEM image of a 1:2 volume ratio shrinking droplet driven by heating at 40°C using the method of the present invention.

[0042] Figure 23 This is an optical side view image of a 1:2 volume ratio shrinking droplet driven by a high-speed camera using the method of this invention at 50°C. The acquisition time was 665 s, with a time interval of 35 s.

[0043] Figure 24 This is an optical top-view image of a 1:2 volume ratio shrinking droplet driven by a high-speed camera using the method of this invention at 50°C. The acquisition time was 665 s, with a time interval of 35 s.

[0044] Figure 25 This is a SEM image of a 1:2 volume ratio shrinking droplet driven by heating at 50°C using the method of the present invention.

[0045] Figure 26 This is an optical side view image of a 1:2 volume ratio shrinking droplet driven by a high-speed camera using the method of this invention at 60°C. The acquisition time is 700s, with a time interval of 50s.

[0046] Figure 27 This is an optical top-view image of a 1:2 volume ratio shrinking droplet driven by a high-speed camera using the method of this invention at 60°C. The acquisition time is 700s, with a time interval of 50s.

[0047] Figure 28This is a SEM image of a 1:2 volume ratio shrinking droplet driven by heating at 60°C using the method of the present invention.

[0048] Figure 29 The method of this invention is used at a 1:1 volume dilution ratio (5.0 × 10⁻⁶). 9 (particles / μL), SEM of the shrinking droplets after heating at 40℃.

[0049] Figure 30 The method of this invention uses a 2:3 volume dilution ratio (4.0 × 10⁻⁶). 9 (particles / μL), SEM of the shrinking droplets after heating at 40℃.

[0050] Figure 31 The method of this invention is used at a volume dilution ratio of 2:5 (2.9 × 10⁻⁶). 9 (particles / μL), SEM of the shrinking droplets after heating at 40℃.

[0051] Figure 32 The method of this invention is used at a volume dilution ratio of 1:3 (2.5 × 10⁻⁶). 9 (particles / μL), SEM of the shrinking droplets after heating at 40℃.

[0052] According to the method of the present invention, the Raman detection results driven at 40°C are more consistent and stable than those driven by natural drying, 30°C, 50°C, and 60°C, as the temperature changes. According to the method of the present invention, at the same temperature, the Raman detection results of the 1:2 dilution group are more consistent and stable than those of the 1:1, 2:3, 2:5, and 1:3 dilution groups, as the concentration of nano-sol particles changes. According to the method of the present invention, Raman detection is more sensitive (with greater signal intensity) under the conditions of 40°C driving and 1:2 dilution of nano-sol particles. Detailed Implementation

[0053] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0054] Reference Figures 1-32 A SERS detection method based on temperature-driven shrinking droplets constructing hotspot-ordered multilayer nanoarrays includes the following steps: Example 1 Step 1: Pretreatment of the silicon wafer substrate using aqua regia, piranha solution, and anhydrous ethanol in that order. Spread a 0.05 M zinc acetate solution evenly onto a 5 mm × 5 mm silicon wafer substrate and dry it in a 65°C oven. Remove the substrate and mix it with 70 mL of zinc nitrate (0.015 M), 70 mL of hexamethylenetetramine (HMT) (0.015 M), and 4 mL of ammonia in a beaker. Place the mixture in an 80°C oven for hydrothermal reaction for 24 hours. Remove the substrate and dry it in a 65°C oven for later use. Step 2: Immerse the substrate in a solution of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) for 1 hour. After the PFDTES evaporates, immerse the substrate again. Repeat this process twice to form a superhydrophobic zinc oxide nanosubstrate. Figure 1 As shown; Step 3: Take 1-10 ml of gold nano-sol into a centrifuge tube, place it in a centrifuge, and centrifuge at 6000-8000 rpm for 10-20 minutes. Remove the tube, discard the supernatant, and collect the concentrated nano-sol from the bottom of the centrifuge tube for later use. The nano-sol particle structure is as follows: Figure 4 As shown; Step 4, prepare 10 -7 -10 -10 M crystal violet aqueous solution; Step 5: Take 10 μL of the concentrated nano-sol from Step 3 and disperse it in deionized water to form a solution containing 10 μL of nano-sol. -7 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 6, analogous to step 5, can be configured to contain 10 -8 M / 10 -9 M / 10 -10 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 7: Take 10 μL of the nanosol particles from Step 6 and drop them onto the substrate from Step 2 to form droplets. Heat the droplets on a 40°C heating plate until they shrink, forming an ordered multilayer nanoarray. Figure 6 As shown; Step 8: Repeat step 7 to perform in-situ SERS detection during the dynamic process of droplet heating and contraction. The detection results are as follows: Figure 6 As shown; Step 9: Circulating convection is generated through the synergistic effect of the Marangoni and coffee ring effects, allowing nanoparticles in the contracted droplet to circulate between the center and edge of the droplet. SERS detection is performed during this process. The excitation wavelength of the Raman spectrometer is 633 nm.

[0055] Comparative Example 1 Step 1: Pretreatment of the silicon wafer substrate using aqua regia, piranha solution, and anhydrous ethanol in that order. Spread a 0.05 M zinc acetate solution evenly onto a 5 mm × 5 mm silicon wafer substrate and dry it in a 65°C oven. Remove the substrate and mix it with 70 mL of zinc nitrate (0.015 M), 70 mL of hexamethylenetetramine (HMT) (0.015 M), and 4 mL of ammonia in a beaker. Place the mixture in an 80°C oven for hydrothermal reaction for 24 hours. Remove the substrate and dry it in a 65°C oven for later use. Step 2: Immerse the substrate in a PFDTES solution for 1 hour. After the PFDTES evaporates, immerse it again. Repeat this process twice to form a superhydrophobic zinc oxide nanosubstrate. Figure 1 As shown; Step 3: Take 1-10 ml of gold nano-sol into a centrifuge tube, place it in a centrifuge, and centrifuge at 6000-8000 rpm for 10-20 minutes. Remove the tube, discard the supernatant, and collect the concentrated nano-sol from the bottom of the centrifuge tube for later use. The nano-sol particle structure is as follows: Figure 4 As shown; Step 4, prepare 10 -7 -10 -9 M crystal violet aqueous solution; Step 5: Take 10 μL of the concentrated nano-sol from Step 3 and disperse it in deionized water to form a solution containing 10 μL of nano-sol. -7 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 6, analogous to step 5, can be configured to contain 10 -8 M / 10 -9 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 7: Take 10 μL of the nano-sol particles from Step 6 and drop them onto the substrate from Step 2 to form droplets. Allow the droplets to dry naturally at room temperature to form a nano-array structure, such as... Figure 6 As shown; Step 8: Repeat step 7 to perform in-situ SERS detection during the dynamic process of droplet contraction. The detection results are as follows: Figure 6 As shown. The excitation wavelength of the Raman spectrometer is 633 nm.

[0056] Comparing Example 1 with Comparative Example 1 (natural drying shrinkage droplet method), it was found that Comparative Example 1 only achieved a detection accuracy of 10 for crystal violet. -9 M, while Example 1 can reach 10 -10 M; such as Figure 6 , 7 Comparative Example 1 ( Figure 7 Compared to Example 1 () Figure 6 The Raman spectra are chaotic, with poor sensitivity and stability.

[0057] Example 2 Step 1: Pretreatment of the silicon wafer substrate using aqua regia, piranha solution, and anhydrous ethanol in that order. Spread a 0.05 M zinc acetate solution evenly onto a 5 mm × 5 mm silicon wafer substrate and dry it in a 65°C oven. Remove the substrate and mix it with 70 mL of zinc nitrate (0.015 M), 70 mL of hexamethylenetetramine (HMT) (0.015 M), and 4 mL of ammonia in a beaker. Place the mixture in an 80°C oven for hydrothermal reaction for 24 hours. Remove the substrate and dry it in a 65°C oven for later use. Step 2: Immerse the substrate in a PFDTES solution for 1 hour. After the PFDTES evaporates, immerse it again. Repeat this process twice to form a superhydrophobic zinc oxide nanosubstrate. Figure 1 As shown; Step 3: Take 1-10 ml of gold nano-sol into a centrifuge tube, place it in a centrifuge, and centrifuge at 6000-8000 rpm for 10-20 minutes. Remove the tube, discard the supernatant, and collect the concentrated nano-sol from the bottom of the centrifuge tube for later use. The nano-sol particle structure is as follows: Figure 4 As shown; Step 4, prepare 10 -7 M crystal violet aqueous solution; Step 5: Take 10 μL of the concentrated nano-sol from Step 3 and disperse it in deionized water to form a solution containing 10 μL of nano-sol. -7 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 6: Take 10 μL of the nano-sol particles from Step 5 and drop them onto the substrate from Step 2 to form droplets. Heat the droplets on a 40°C heating plate until they shrink, forming an ordered multilayer nanoarray. Figure 6 As shown; Step 7: Repeat step 6 to perform in-situ SERS detection during the dynamic process of droplet heating and contraction. The detection results are as follows: Figure 8 As shown; Step 9: Circulating convection is generated through the synergistic effect of the Marangoni and coffee ring effects, allowing nanoparticles in the contracted droplet to circulate between the center and edge of the droplet. SERS detection is performed during this process. The excitation wavelength of the Raman spectrometer is 633 nm.

[0058] Comparative Example 2 Step 1: Pretreatment of the silicon wafer substrate using aqua regia, piranha solution, and anhydrous ethanol in that order. Spread a 0.05 M zinc acetate solution evenly onto a 5 mm × 5 mm silicon wafer substrate and dry it in a 65°C oven. Remove the substrate and mix it with 70 mL of zinc nitrate (0.015 M), 70 mL of hexamethylenetetramine (HMT) (0.015 M), and 4 mL of ammonia in a beaker. Place the mixture in an 80°C oven for hydrothermal reaction for 24 hours. Remove the substrate and dry it in a 65°C oven for later use. Step 2: Immerse the substrate in a PFDTES solution for 1 hour. After the PFDTES evaporates, immerse it again. Repeat this process twice to form a superhydrophobic zinc oxide nanosubstrate. Figure 1 As shown; Step 3: Take 1-10 ml of gold nano-sol into a centrifuge tube, place it in a centrifuge, and centrifuge at 6000-8000 rpm for 10-20 minutes. Remove the tube, discard the supernatant, and collect the concentrated nano-sol from the bottom of the centrifuge tube for later use. The nano-sol particle structure is as follows: Figure 4 As shown; Step 4, prepare 10 -7 M crystal violet aqueous solution; Step 5: Take 10 μL of the concentrated nano-sol from Step 3 and disperse it in deionized water to form a solution containing 10 μL of nano-sol. -7 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 6: Take 10 μL of the nano-sol particles from Step 5 and drop them onto the substrate from Step 2 to form droplets. Allow the droplets to dry naturally at room temperature to form a nano-array structure, such as... Figure 7 As shown; Step 7: Repeat step 6 to perform in-situ SERS detection during the dynamic process of droplet contraction. The detection results are as follows: Figure 8 As shown; Step 8: Repeat step 7 to perform in-situ SERS detection during the dynamic process of droplet contraction. The detection results are as follows: Figure 6 As shown. The excitation wavelength of the Raman spectrometer is 633 nm.

[0059] Comparing Example 2 and Comparative Example 2 (natural drying shrinkage droplet method), it was found that the optimal temperature was 40°C; Comparative Example 2 ( Figure 8 , 12 Compared to Example 2 () Figure 8 , 10 11) The Raman spectra showed poor sensitivity and stability; at different temperatures, the Raman detection results of the 40℃ group were more sensitive and stable than those of other groups.

[0060] Example 3 Step 1: Pretreatment of the silicon wafer substrate using aqua regia, piranha solution, and anhydrous ethanol in that order. Spread a 0.05M zinc acetate solution evenly onto a 5mm × 5mm silicon wafer substrate and dry it in a 65℃ oven. Remove the substrate and mix it with 70mL of zinc nitrate (0.015M), 70mL of hexamethylenetetramine (HMT) (0.015M), and 4mL of ammonia in a beaker. Place the mixture in an 80℃ oven for hydrothermal reaction for 24 hours. Remove the substrate and dry it in a 65℃ oven for later use. Step 2: Immerse the substrate in a PFDTES solution for 1 hour. After the PFDTES evaporates, immerse it again. Repeat this process twice to form a superhydrophobic zinc oxide nanosubstrate. Figure 1 As shown; Step 3: Take 1-10 ml of gold nano-sol into a centrifuge tube, place it in a centrifuge, and centrifuge at 6000-8000 rpm for 10-20 minutes. Remove the tube, discard the supernatant, and collect the concentrated nano-sol from the bottom of the centrifuge tube for later use. The nano-sol particle structure is as follows: Figure 4 As shown; Step 4, prepare 10 -7 M crystal violet aqueous solution; Step 5: Take 10 μL of the concentrated nano-sol from Step 3 and disperse it in deionized water to form a solution containing 10 μL of nano-sol. -7 1:2 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 6: Take 10 μL of the nano-sol particles from Step 5 and drop them onto the substrate from Step 2 to form droplets. Heat the droplets on a 40°C heating plate until they shrink, forming an ordered multilayer nanoarray. Figure 6 As shown; Step 7: Repeat step 6 to perform in-situ SERS detection during the dynamic process of droplet heating and contraction. The detection results are as follows: Figure 8 As shown; Step 9: Circulating convection is generated through the synergistic effect of the Marangoni and coffee ring effects, allowing nanoparticles in the contracted droplet to circulate between the center and edge of the droplet. SERS detection is performed during this process. The excitation wavelength of the Raman spectrometer is 633 nm.

[0061] Comparative Example 3 Step 1: Pretreatment of the silicon wafer substrate using aqua regia, piranha solution, and anhydrous ethanol in that order. Spread a 0.05 M zinc acetate solution evenly onto a 5 mm × 5 mm silicon wafer substrate and dry it in a 65°C oven. Remove the substrate and mix it with 70 mL of zinc nitrate (0.015 M), 70 mL of hexamethylenetetramine (HMT) (0.015 M), and 4 mL of ammonia in a beaker. Place the mixture in an 80°C oven for hydrothermal reaction for 24 hours. Remove the substrate and dry it in a 65°C oven for later use. Step 2: Immerse the substrate in a PFDTES solution for 1 hour. After the PFDTES evaporates, immerse it again. Repeat this process twice to form a superhydrophobic zinc oxide nanosubstrate. Figure 1 As shown; Step 3: Take 1-10 ml of gold nano-sol into a centrifuge tube, place it in a centrifuge, and centrifuge at 6000-8000 rpm for 10-20 minutes. Remove the tube, discard the supernatant, and collect the concentrated nano-sol from the bottom of the centrifuge tube for later use. The nano-sol particle structure is as follows: Figure 4 As shown; Step 4, prepare 10 -7 M crystal violet aqueous solution; Step 5: Take 10 μL of the concentrated nano-sol from Step 3 and disperse it in deionized water to form a solution containing 10 μL of nano-sol. -7 1:3 dilution of M crystal violet aqueous solution into nanoparticle sol; Step 6: Take 10 μL of the nano-sol particles from Step 5 and drop them onto the substrate from Step 2 to form droplets. Heat the droplets on a 40°C heating plate until they shrink, forming an ordered multilayer nanoarray. Figure 6 As shown; Step 7: Repeat step 6 to perform in-situ SERS detection during the dynamic process of droplet heating and contraction. The detection results are as follows: Figure 8 As shown; Comparing Example 3 and Comparative Example 3 (1:3 volume dilution ratio), the optimal volume dilution ratio was found to be 1:2; Figure 9 Compared to Example 3, Comparative Example 3 showed poorer sensitivity and stability in Raman spectra. At different volume dilution ratios, the Raman detection results of the 1:2 group were more sensitive and more stable than those of the other groups.

[0062] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays, characterized in that, The thermocapillary effect or Marangoni effect is generated by changing the surface tension of the gas-liquid interface through temperature changes, thereby regulating the dynamic process of nanosol droplet contraction. This allows target molecules to be actively transported into a uniformly distributed hot spot ordered multilayer nanoarray structure, avoiding the formation of coffee rings due to the decrease in nanoarray uniformity. The target signal is then detected by Raman spectroscopy. The temperature range is 30-50℃.

2. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 1, characterized in that, The ordered multilayer nanoarray is obtained by convective autonomous assembly driving the directional deposition of nanoparticles on a substrate to form nanoscale hot spots.

3. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 1, characterized in that, The method for temperature-driven contraction to construct droplet hotspots includes the following steps: Preparation of superhydrophobic zinc oxide nanosubstrates; The concentrated nanosol at the bottom of the metal nanosol was collected by centrifugation; Concentrated nanosol is dispersed in water to form a sol of nanoparticles; Nanoparticle sol and target molecules are formed into shrinking droplets on a superhydrophobic zinc oxide nanosubstrate, and under temperature-driven conditions, an ordered multilayer nanoarray is formed.

4. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 3, characterized in that, The metal nanosol includes at least one of silver nanosol, gold nanosol, and copper nanosol.

5. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 3, characterized in that, The superhydrophobic zinc oxide nanosubstrate substrate material is a planar material with a flat surface suitable for loading nanoparticles, including at least one of silicon wafers, mica sheets, and glass sheets.

6. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 1, characterized in that, The nanoarray generates cyclic convection through the synergistic effect of the Marangoni and coffee ring effects.

7. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 3, characterized in that, The concentrated nanoparticle sol and target molecules were formed into shrinking droplets on a superhydrophobic zinc oxide nanosubstrate. Under temperature drive of 30-50℃, an ordered multilayer nanoarray was formed. By controlling the temperature and nanoparticle concentration, the shrinkage dynamic process of the nanosol droplets was detected in the hot spot and the SERS signal was detected.

8. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 1, characterized in that, The target substance includes at least one of plasticizers, organic pollutants, antitumor drugs, toxins, pesticide residues, dyes, antibiotics, explosives, and amino acids, and the solution of the target substance is an aqueous solution or an organic solution.

9. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 1, characterized in that, The target substance is a dye.

10. The SERS detection method based on temperature-driven contraction droplet construction of hotspot-ordered multilayer nanoarrays according to claim 1, characterized in that, The target substance includes at least one of crystal violet, malachite green, Nile blue, methylene blue, rhodamine, brilliant green, and nylon blue.

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