A method for preparing a gold nanorod multi-morphology array enhanced Raman spectroscopy substrate

Abstract

This application relates to a method for preparing gold nanorod multimorphic arrays to enhance Raman spectroscopy substrates, specifically in the field of optical detection structure fabrication. Due to the different surface potential energy differences experienced by gold nanorod particles on substrates with varying roughness, monodisperse gold nanorod particles are assembled into arrays of different morphologies. The gold nanorod multimorphic array structures have different nano-intervals, forming "hot spots" of varying density under external light field excitation. These "hot spots" are distributed with localized electromagnetic fields of varying intensities. When probe molecules are adsorbed onto the surface of the gold nanorod array structure, the incident and emitted light fields of the Raman scattering process are enhanced differently due to resonance with localized surface plasmon modes. This invention has promising applications in the field of spectral detection sensor fabrication.

Description

Technical Field

[0001] This application relates to the field of optical detection structure fabrication, specifically to a method for fabricating a gold nanorod array strong Raman spectroscopy substrate. Background Technology

[0002] SERS detection technology based on noble metal nanostructures offers advantages such as fingerprint-like feature detection and non-destructive testing, and is often used to detect harmful substances such as environmental pollutants and food additives. Precise and controllable self-assembly of nanoparticles has always been a research hotspot. SERS substrates prepared by physical or chemical methods exhibit high sensitivity, high reproducibility, and good stability. Therefore, developing effective, inexpensive, and convenient methods for the controlled self-assembly of nanosubstrates remains a research topic. Utilizing their unique optical response characteristics to effectively control the optical signals of probe molecules has significant scientific research value and engineering application potential.

[0003] In fact, self-assembled substrate fabrication methods are becoming increasingly widely used. Specifically, self-assembly is the process by which nanoparticles in a chaotic system ultimately form an ordered system through specific interactions (attraction, repulsion, and chemical bonds) with other system components. Substrates prepared using self-assembly are easy to control and inexpensive, making them suitable for large-scale applications and widespread adoption.

[0004] However, research shows that the effectiveness of self-assembled substrates depends on the properties of the nanoparticles (shape, size, and material, etc.), the interactions between nanoparticles, and the interactions between nanoparticles and the excitation wavelength. In current technologies, it is difficult to fabricate various metal micro / nanostructures with diverse morphologies on a single substrate at low cost to meet the needs of different molecules and excitation wavelengths. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a method for preparing a gold nanorod array-enhanced Raman spectroscopy substrate. The specific technical solution adopted is as follows:

[0006] High-precision sandpaper is used to polish the silicon wafer substrate. During the polishing process, the polishing time and polishing area need to be controlled, and polished areas, transition areas and unpolished areas are formed on the whole silicon wafer.

[0007] After cleaning the polished substrate, gold nanorod colloid is dropped onto the cleaned substrate. The unassembled substrate is placed in a specific container and kept in a constant temperature and humidity environment.

[0008] Gold nanorod colloids form a vertical array under molecular forces in the unpolished area and a planar array under the influence of additional surface force differences in the polished area, thus generating a multimorphic array of gold nanorods on the entire substrate surface.

[0009] Optionally, the step of setting the gold nanorod particles onto the cleaned substrate includes:

[0010] The sodium borocyanide solution was prepared by dissolving sodium borocyanide crystals in deionized water.

[0011] The chloroauric acid solution was prepared by dissolving chloroauric acid tetrahydrate crystals in deionized water.

[0012] A solution of hexadecyltrimethylamine bromide was prepared by dissolving hexadecyltrimethylamine bromide crystals in deionized water;

[0013] A silver nitrate solution was prepared by dissolving silver nitrate crystals in deionized water.

[0014] The ascorbic acid solution is prepared by dissolving ascorbic acid crystals in deionized water.

[0015] Optionally, after the step of dissolving ascorbic acid crystals in deionized water to prepare the ascorbic acid solution, the method further includes:

[0016] Add the predetermined amount of hexadecyltrimethylamine bromide to a deionized aqueous solution and heat and stir.

[0017] Chloroauric acid and sodium borohydride solutions in preset proportions were added to the deionized aqueous solution to obtain a seed solution, which was then stored at a constant temperature.

[0018] Add the predetermined amount of hexadecyltrimethylamine bromide solution to the deionized water solution and heat and stir.

[0019] Add the chloroauric acid solution, silver nitrate solution, hydrochloric acid solution and ascorbic acid solution in the predetermined proportions to the above deionized water solution in sequence and heat and stir.

[0020] Add the preset amount of seed solution to the above solution, heat and stir to obtain gold nanorod particle colloid.

[0021] Optionally, the substrate can be cleaned and polished by sequentially ultrasonically cleaning the substrate surface with acetone, ethanol, and deionized water.

[0022] Alternatively, when polishing the substrate with sandpaper, high-precision sandpaper can be selected to physically polish certain areas.

[0023] Optionally, the high-precision sandpaper has a grit of 12,000 and the sanding time is 2 minutes.

[0024] Optionally, the substrate is placed in a container and kept at a constant temperature of 25°C and humidity of 50%-60%.

[0025] Optionally, the substrate is a silicon wafer.

[0026] Optionally, before sanding the substrate with sandpaper, the process also includes cutting the substrate to a preset size.

[0027] The beneficial effects of this invention are:

[0028] Because gold nanorod particles experience unequal surface potential differences on dielectric layers with varying roughness, monodisperse gold nanorod particles are assembled into multimorphic arrays of gold nanorods in different regions. Therefore, during evaporation, the colloidal gold nanorod particles generate a multimorphic array of gold nanorods to enhance Raman spectroscopy. Pre-defined probe molecules are deposited on the surface of the multimorphic gold nanorod array structure. Since different assembly structures of gold nanorods form "hot spots" of varying density under external light field excitation, these "hot spots" have extremely strong local electromagnetic fields. When probe molecules are adsorbed onto the surface of the gold nanorod array structure (near-field region), the incident and emitted light fields of their Raman scattering process (especially those located at the "hot spots") are enhanced due to resonance with the local surface plasmon modes. Therefore, Raman scattered light of varying intensities from the probe molecules can be received in the far-field region. This invention only requires sandpaper polishing and setting up a colloidal gold nanorod particle array to prepare gold nanorod arrays of different morphologies; the preparation process is simple, fast, and low-cost. In addition, no other organic substances are introduced during the preparation process, which is beneficial for high-accuracy molecular detection and has good application prospects in sensors, single-particle statistics and other optoelectronic devices based on surface-enhanced Raman scattering spectroscopy. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of a method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to an embodiment of the present invention;

[0031] Figure 2 Scanning electron microscope images of the prepared gold nanorod multimorphic array enhanced Raman spectroscopy substrate: (ab) vertical array (unpolished area); (cd) transition array (transition region); (ef) planar array (polished area);

[0032] Figure 3 The substrates provided for embodiments of this application are Raman spectra of different concentrations of rhodamine molecules and intensity comparison diagrams: (a) vertical array; (b) transition array; (c) tiled array; (d) comparison diagram of Raman detection intensity of rhodamine molecules using multi-morphology arrays;

[0033] Figure 4 The Raman spectra of crystal violet molecules at different concentrations provided for embodiments of this application are as follows: (a) vertical array; (b) transition array; (c) planar array; (d) comparison of Raman detection intensity of crystal violet molecules by multi-morphology array.

[0034] Figure 5 Raman spectra and intensity comparison line graphs of rhodamine and crystal violet molecules on the substrate provided in this application under different wavelength excitation conditions: (ab) Rhodamine molecule; (cd) Crystal violet molecule. Detailed Implementation

[0035] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0036] Figure 1 This is a flowchart illustrating a method for preparing a gold nanorod multimorphic array-enhanced Raman spectroscopy substrate according to an embodiment of the present invention. For ease of understanding, the method of this application is described in detail below, and for convenience, the method for preparing the gold nanorod multimorphic array-enhanced Raman spectroscopy substrate is simply referred to as the "method," which includes:

[0037] S101. The substrate is polished using high-precision sandpaper.

[0038] Cut the silicon wafer substrate to the target size (10×5mm) 2 High-precision sandpaper was used to polish a portion of a silicon wafer substrate for a fixed period of time. The polished and unpolished areas exhibited different visual effects. When polishing the substrate, high-precision sandpaper with a grit of 12000 was selected for physical polishing of a specific area. The polishing time was 2 minutes.

[0039] S102. Clean and polish the substrate, and then place the gold nanorod particles onto the cleaned substrate.

[0040] The polished silicon substrate was ultrasonically cleaned sequentially with acetone, alcohol, and deionized water. Then, gold nanorod colloids were placed on the polished silicon substrate, ensuring the gold nanorod colloids were dispersed in both the unpolished and polished areas. Specifically, the volume of the gold nanorods needed to match the target specifications of the silicon substrate and the polished area on the substrate. No specific limitation is made here; for clarity, a space of 3 μL on the silicon substrate is used as an example. Specifically, the physically polished silicon substrate was ultrasonically cleaned in acetone to remove organic impurities from the substrate surface. Since acetone is soluble in ethanol, the substrate ultrasonically cleaned with acetone was then placed in an ultrasonic cleaning device filled with ethanol to remove acetone and other impurities from the substrate surface. Since ethanol and water are miscible in any proportion, the substrate cleaned with ethanol was placed in an ultrasonic cleaning device filled with deionized water. Finally, it was dried in a clean oven until ready for use.

[0041] S103. The substrate is placed in a container, and the gold nanorod particle colloid generates a gold nanorod multimorph array under the action of surface force difference.

[0042] The colloid provides the necessary constant temperature and humidity environment, which consists of two nested beakers of different sizes. Inside each beaker is a platform for placing a silicon wafer substrate. An appropriate volume of gold nanorod colloid is dropped onto the silicon wafer substrate and placed on the platform, with half of the gold nanorod colloid positioned in the unpolished area and the other half in the polished area. The platform and the silicon wafer containing the gold nanorod colloid are placed in the larger beaker, and an appropriate amount of water is added. The smaller beaker is then nested inside to maintain a sealed environment under constant temperature and humidity. During the evaporation process, gold nanorod colloids are subjected to varying surface potential differences in different regions under dielectric layer regulation. Monodisperse gold nanorods are assembled into multimorphic arrays, resulting in adjacent gold nanorods forming a vertical array "edge-to-edge" in the unpolished areas of the silicon substrate and a horizontal array "end-to-end" in the polished areas. The edge capillary flow generated during the actual assembly process carries gold nanorods and hexadecyltrimethylamine bromide (CTAB) molecules to the droplet edge, leading to an increase in CTAB molecule concentration at the meniscus. This creates a significant concentration difference between the droplet edge and center, generating centripetal capillary force that pulls particles towards the solution center. Without additional forces, the particles exhibit a vertical array arrangement. However, due to changes in the dielectric layer configuration, a large number of CTAB molecules on the gold nanorod surface are squeezed into the solution environment, leaving only a small number of CTAB molecules in the "grooves" of the assembled surface. Therefore, a concentration difference of CTAB molecules is generated in the spatial region above and below the particles, which in turn creates a surface potential difference that exerts an additional force on the particles, suppressing them from flowing further towards the center of the solution and causing them to remain at the meniscus. After the solution is completely dried, a flat array is formed, thus obtaining the gold nanorod multimorphic array structure substrate of this application. Specifically, the gold nanorod colloid evaporation environment is fixed at a temperature of 25°C and a humidity of 50%-60%. Optionally, the evaporation time of the gold nanorod colloid is determined according to actual needs. Generally, the time standard is the formation of the gold nanorod multimorphic array structure after the gold nanorod colloid is completely dried under the control of the dielectric layer.

[0043] Gold nanorods typically carry surface protectants that provide the molecular forces required for their assembly. Since temperature and humidity play crucial roles in self-assembly, controlling the self-assembly conditions can effectively avoid the "coffee ring" effect and induce Marangoni flow under suitable conditions, resulting in a more ordered distribution of gold nanorods. Ultimately, a vertical array of hexagonal gold nanorods was formed at the unpolished areas of the silicon wafer, while at the polished areas, changes in the dielectric layer structure led to a planar array of gold nanorods, resulting in a large-area, uniformly deposited array of multi-morphological gold nanorods on the silicon wafer. The formation of the vertical array requires a balance of multiple forces. Van der Waals forces and depletion forces provide attraction, while electrostatic forces provide repulsion. When these three forces are balanced, a vertical array of gold nanorods is formed. Van der Waals forces and depletion forces tightly bind adjacent gold nanorods together, while electrostatic repulsion stabilizes them within a certain distance, preventing random aggregation. However, at the polished silicon wafer interface, changes in the dielectric layer structure lead to a balance of the three destructive forces, resulting in different planar arrays of gold nanorods. Specifically, when the gold nanorods are of suitable size, interaction forces arise between the gold nanorods and the high-roughness silicon substrate. As the grooves on the silicon surface attract the gold nanorods, CTAB molecules in the solution and on the nanoparticle surface are more distributed outside the grooves. Changes in the dielectric layer structure cause a density difference in surfactant molecules around the nanoparticles, resulting in a potential energy difference in the overall structure. This disrupts the three-force balance during the self-assembly process of the gold nanorods, causing them to tend to lay flat even under suitable evaporation self-assembly conditions. Furthermore, it should be noted that the dielectric layer modulation application time should not be too long or too short to obtain good morphology. Experiments have shown that a dielectric layer modulation application time of 3 days is optimal. By changing the substrate configuration, the magnitude of the forces acting on the particles during assembly is altered, disrupting the conditions for the formation of a single-morphology array. This allows for the fabrication of vertical arrays with a "hexagonal" structure, well-morphologically sound flat arrays, and transitional arrays exhibiting a collapsing tendency in their vertical structures.

[0044] This invention uses high-precision sandpaper to treat a portion of the silicon wafer surface, damaging the oxide layer and altering the substrate surface configuration. Gold nanorod particles are then assembled on this substrate. The SEM characterization results of the assembled substrate are shown below. Figure 2 As shown, three locations were selected on the silicon wafer: an unpolished area, a transition area, and a polished area. The assembly morphology differed significantly across these different areas. For example... Figure 2 As shown in (a, c, e), under relatively low magnification, the gold nanorod array in the unpolished region exhibits an "island"-like distribution, the distribution structure in the polished region shows no obvious pattern, and the particle distribution structure in the transition region (located at the boundary between the polished and unpolished regions) is intermediate between the two. Figure 2As shown in (b), (d), and (f), under high magnification, the gold nanorods in the unpolished region exhibit a vertical array distribution with small interparticle gaps and a neat arrangement. In the polished region, the particles show a planar array distribution, but the interparticle gaps are larger. Furthermore, in the transition region, the gold nanorods still exhibit a vertical arrangement, but their array morphology tends to collapse. Assembling gold nanorods in three different configuration regions results in different assembly morphologies and density distributions. These different assembly morphologies and density distributions facilitate surface-enhanced Raman scattering (SERS) tests for different molecules and different excitation wavelengths.

[0045] This invention uses silicon wafers as the substrate. Silicon wafers, as a common self-assembly substrate, have the advantages of low cost, easy polishing and cleaning. Silicon wafers require a certain thickness of surface oxide layer. Through physical polishing, the unpolished areas and polished areas have different dielectric layer environments and surface structures, resulting in different assembly morphologies of the particles.

[0046] This invention uses 12,000-grit sandpaper. High-precision sandpaper makes it easier to match the structure obtained from polishing silicon wafers with the selected particle size. Lower-grit sandpaper produces larger "grooves," leading to large-area particle clusters. The polishing time is strictly controlled during the polishing process, with a fixed polishing time of 3 minutes. Obvious scratches were observed under a 50x optical microscope objective.

[0047] After preparing a substrate for enhanced Raman scattering spectroscopy, a pre-defined probe molecule is deposited on the surface of the gold nanorod multimorphic array structure using a deposition method. Optionally, the pre-defined probe molecule can be either rhodamine or crystal violet, without specific limitation. Under the excitation of an external light field, the Raman scattering process of the probe molecule adsorbed on the surface of the gold nanorod multimorphic array structure is enhanced due to the resonance of local surface plasmon modes, thus achieving the effect of enhancing the Raman signal. Depositing the pre-defined probe molecule on the surface of the gold nanorod multimorphic array structure using a deposition method results in a structural layer formed by probe molecules on the surface of the gold nanorod multimorphic array structure on the pre-defined substrate.

[0048] To further illustrate the enhancement effect of the substrate of the present invention on the Raman signal of probe molecules, the applicant tested the Raman signals of rhodamine and crystal violet molecules. The results showed that the substrate prepared in this invention exhibits different particle array morphologies, which, under the excitation of incident light, form differentiated electromagnetic "hot spots," enhancing the Raman scattering of probe molecules in the near-field region and producing results of different intensities in different regions.

[0049] Figure 3 Raman spectra and intensity comparison diagrams of substrates with different concentrations of rhodamine provided in embodiments of this application. Figure 3As shown, the detection limit concentration of rhodamine molecules for the vertical array and the transition array is 10. -10 M, the detection limit concentration of the tiled array is 10. -10 However, the Raman spectral intensity is relatively low at this concentration. Therefore, from the perspective of the detection limit, the detection results of the vertical array and the transition array are better than those of the tiled array. As the concentration of the probe molecule decreases, the enhancement intensity of the three arrays for the rhodamine molecule also decreases, but the Raman signal intensity of the vertical array is greater than that of the transition array, which is greater than that of the tiled array. The Raman relative intensity change (line graph) also shows a similar effect.

[0050] Figure 4 Raman spectra and intensity comparison diagrams of substrates with different concentrations of crystal violet provided in embodiments of this application. Figure 4 As shown, the detection limit for crystal violet molecules is 10 for all three morphological arrays. -8 M, where the tiled array pairs are 10 -8 The detection intensity of crystal violet molecules in M ​​is the result after a 2x magnification. The relative intensity change in the Raman spectrum is similar to the detection results for rhodamine molecules. The detection capability of multi-morphology arrays for crystal violet molecules is as follows: vertical arrays are superior to transition arrays, which are superior to tiled arrays.

[0051] Figure 5 Raman spectra and intensity comparisons of rhodamine and crystal violet molecules on the substrate provided in this application under different wavelength excitation conditions. Figure 5 As shown, rhodamine and crystal violet molecules were selected as the detected molecules. Under different wavelength excitation conditions, opposite experimental patterns emerged between the vertical array and the planar array. At 532 nm excitation, the vertical array showed better enhancement of the probe molecules than the planar array; however, at 785 nm excitation, the enhancement effect of the vertical array was weaker than that of the planar array. It is noteworthy that while the excitation power increased at 785 nm, the enhancement effect produced by the same array was always weaker than that at 532 nm. Therefore, the substrate of this invention can be selected with different excitation wavelengths to obtain Raman signals with different intensities.

[0052] The following solution preparation steps are included before the step of setting gold nanorod particles onto the cleaned substrate during substrate preparation:

[0053] (1) A sodium borocyanide solution is prepared by dissolving sodium borocyanide crystals in deionized water. Specifically, sodium borohydride crystals are dissolved in a pre-set container containing deionized water and subjected to an ice bath to prevent excessive decomposition, thereby obtaining a sodium borohydride solution in the pre-set container.

[0054] (2) A chloroauric acid solution is prepared by dissolving chloroauric acid tetrahydrate crystals in deionized water. Specifically, chloroauric acid tetrahydrate crystals are dissolved in a pre-set container containing deionized water, thereby obtaining a chloroauric acid solution in the pre-set container.

[0055] (3) A hexadecyltrimethylamine bromide solution is prepared by dissolving hexadecyltrimethylamine bromide crystals in deionized water. Specifically, hexadecyltrimethylamine bromide crystals are dissolved in a pre-set container containing deionized water, and the pre-set container is heated and stirred to obtain a hexadecyltrimethylamine bromide solution.

[0056] (4) Silver nitrate crystals are dissolved in deionized water to prepare a silver nitrate solution. Specifically, silver nitrate crystals are dissolved in a pre-set container containing deionized water to obtain a silver nitrate solution.

[0057] (5) An ascorbic acid solution is prepared by dissolving ascorbic acid crystals in deionized water. Specifically, ascorbic acid crystals are dissolved in a pre-set container containing deionized water, thereby obtaining an ascorbic acid solution in the pre-set container.

[0058] After preparing the solution, the following steps are also included in preparing the gold nanorod particle colloid:

[0059] (1) Add the preset amount of hexadecyltrimethylamine bromide to the deionized water solution and heat and stir.

[0060] Hexadecyltrimethylamine bromide crystals were dissolved in a pre-designed container containing deionized water. The container was heated and stirred to obtain a hexadecyltrimethylamine bromide solution. The reaction temperature was maintained by a water bath to ensure the reaction proceeded normally. The temperature of the magnetic stirrer should not be lower than 35°C, but this is not specifically limited. For clarity, the water bath temperature in this experiment is 35°C. In practical applications, one part hexadecyltrimethylamine bromide crystals is 0.292 g, and one part deionized water is 8 mL. The specific ratio of one part hexadecyltrimethylamine bromide crystals to one part deionized water is selected according to actual needs and is not specifically limited. For ease of explanation, this is described as one part hexadecyltrimethylamine bromide crystals and one part deionized water, i.e., 0.292 g of hexadecyltrimethylamine bromide (CTAB) crystals are dissolved in 8 mL of deionized water to prepare a 0.1 mol / L hexadecyltrimethylamine bromide solution.

[0061] (2) Add chloroauric acid and sodium borohydride solutions in a preset ratio to the deionized water solution to obtain a seed solution, and store it at a constant temperature.

[0062] 200 μL of sodium borohydride solution and 48 μL of chloroauric acid solution were added sequentially to hexadecyltrimethylamine bromide solution and heated and stirred to obtain a seed solution. In practical applications, one part of chloroauric acid tetrahydrate crystals is 0.036g, and one part of deionized water is 10mL. The specific ratio of one part chloroauric acid tetrahydrate crystals to one part deionized water is selected according to actual needs. Similarly, one part of sodium borocyanide crystals is 0.019g, and one part of deionized water is 5mL. The specific ratio of one part sodium borocyanide crystals to one part deionized water is also selected according to actual needs and is not specifically limited here. For ease of explanation, the following describes the ratio of sodium borocyanide and chloroauric acid tetrahydrate crystals to deionized water: dissolving 0.036g of chloroauric acid tetrahydrate (HAuCl4·4H2O) crystals in 10mL of deionized water to prepare a 0.01mol / L chloroauric acid solution, and dissolving 0.019g of sodium borocyanide crystals in 10mL of deionized water to prepare a 0.01mol / L sodium borocyanide solution.

[0063] (3) Add the preset amount of hexadecyltrimethylamine bromide solution to the deionized water solution and heat and stir.

[0064] In practical applications, one part of hexadecyltrimethylamine bromide crystals is 0.73g, and one part of deionized water is 20mL. The ratio of one part of hexadecyltrimethylamine bromide crystals to one part of deionized water is specified. The specific amounts of hexadecyltrimethylamine bromide crystals and deionized water are selected according to actual needs and are not specifically limited here. For ease of explanation, this example uses one part each of hexadecyltrimethylamine bromide crystals and deionized water. That is, 0.73g of hexadecyltrimethylamine bromide (CTAB) crystals are dissolved in 20mL of deionized water to prepare the second batch of hexadecyltrimethylamine bromide solution.

[0065] (4) Add the chloroauric acid solution, silver nitrate solution, hydrochloric acid solution and ascorbic acid solution in the preset proportions to the above deionized water solution in sequence and heat and stir.

[0066] Chloroauric acid tetrahydrate crystals are dissolved in a pre-prepared container containing deionized water to obtain a chloroauric acid solution. In practical applications, one part of chloroauric acid tetrahydrate crystals is 0.036 g, and one part of deionized water is 10 mL, with a ratio of one part chloroauric acid crystals to one part deionized water; one part of silver nitrate crystals is 0.017 g, and one part of deionized water is 10 mL, with a ratio of one part chloroauric acid crystals to one part deionized water; one part of ascorbic acid crystals is 0.0352 g, and one part of deionized water is 2 mL, with a ratio of one part ascorbic acid crystals to one part deionized water. The specific amounts of ascorbic acid crystals and deionized water are selected according to actual needs. 2 mL of chloroauric acid solution, 200 μL of silver nitrate solution, 130 μL of hydrochloric acid solution, and 160 μL of ascorbic acid solution are sequentially added to the prepared second batch of hexadecyltrimethylamine bromide solution, and the mixture is heated and stirred to obtain the growth solution. The specific amounts of tetrahydrate chloroauric acid crystals, silver nitrate crystals, ascorbic acid crystals, and deionized water used are selected according to actual needs and are not specifically limited here. For ease of explanation, the following describes the ratios of tetrahydrate chloroauric acid crystals and ascorbic acid crystals to deionized water: 0.036g of tetrahydrate chloroauric acid (HAuCl4·4H2O) crystals are dissolved in 10mL of deionized water to prepare a 0.01mol / L chloroauric acid solution; 0.017g of ascorbic acid crystals are dissolved in 10mL of deionized water to prepare a 0.01mol / L silver nitrate solution; and 0.0352g of ascorbic acid crystals are dissolved in 2mL of deionized water to prepare a 0.01mol / L sodium borocyanide solution.

[0067] (5) Add the preset amount of seed solution to the above solution and heat and stir to obtain gold nanorod particle colloid.

[0068] The pre-prepared seed solution was poured into the growth solution and heated with stirring. Afterward, it was grown at a constant temperature of 30°C for 12 hours to obtain gold nanorod colloids. It should be noted that to ensure a complete reaction without damaging the morphology and dispersibility of the synthesized gold nanorods, the growth time should not be too short or too long, depending on the reactant concentration and reaction environment. No specific limit is made here; for clarity, 12 hours is used. Following this step, to ensure a complete reaction, one or more reactants are usually set in excess. Therefore, centrifugation with deionized water is necessary to remove excess reagents. To ensure thorough washing without damaging the CTAB protective agent on the surface of the gold nanorods, the number of centrifugations should be neither too many nor too few. Experiments have shown that three centrifugations are optimal.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a gold nanorod multimorphic array-enhanced Raman spectroscopy substrate, characterized in that, The method includes: The substrate is polished using sandpaper; the substrate is a silicon wafer; the polishing time and polishing area need to be controlled during the polishing process, and polished area, transition area and unpolished area are formed on the whole silicon wafer; After cleaning and polishing the substrate, gold nanorod colloids are dropped onto the cleaned substrate. When a substrate is placed in a container, the gold nanorod particles form a multimorphic array of gold nanorods under the influence of molecular forces.

2. The method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to claim 1, characterized in that, Prior to the step of setting gold nanorod particles onto a cleaned substrate, the following steps are included: The sodium borocyanide solution was prepared by dissolving sodium borocyanide crystals in deionized water. The chloroauric acid solution was prepared by dissolving chloroauric acid tetrahydrate crystals in deionized water. A solution of hexadecyltrimethylamine bromide was prepared by dissolving hexadecyltrimethylamine bromide crystals in deionized water; A silver nitrate solution was prepared by dissolving silver nitrate crystals in deionized water. The ascorbic acid solution is prepared by dissolving ascorbic acid crystals in deionized water.

3. The method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to claim 2, characterized in that, Following the step of preparing the ascorbic acid solution by dissolving ascorbic acid crystals in deionized water, the following steps are also included: Add the predetermined amount of hexadecyltrimethylamine bromide to a deionized aqueous solution and heat and stir. Chloroauric acid and sodium borohydride solutions in preset proportions were added to the deionized aqueous solution to obtain a seed solution, which was then stored at a constant temperature. Add the predetermined amount of hexadecyltrimethylamine bromide solution to the deionized water solution and heat and stir. Add the chloroauric acid solution, silver nitrate solution, hydrochloric acid solution and ascorbic acid solution in the predetermined proportions to the above deionized water solution in sequence and heat and stir. Add the preset amount of seed solution to the above solution, heat and stir to obtain gold nanorod particle colloid.

4. The method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to claim 1, characterized in that, The cleaning method for the polished substrate is to ultrasonically clean the substrate surface sequentially with acetone, ethanol and deionized water.

5. The method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to claim 1, characterized in that, When polishing a substrate with high-precision sandpaper, select a portion of the substrate for physical polishing.

6. The method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to claim 5, characterized in that, The high-precision sandpaper has a mesh size of 12000 and a sanding time of 2 minutes.

7. The method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to claim 1, characterized in that, Place the substrate in a container and maintain a constant temperature of 25°C and humidity of 50%-60%.

8. A method for preparing a gold nanorod multimorphic array enhanced Raman spectroscopy substrate according to any one of claims 1-7, characterized in that, Before sanding the substrate with sandpaper, the process also includes cutting the substrate to a preset size.

Images