Substrates for trace detection, substrate preparation methods and their applications

Abstract

The present disclosure provides a substrate for surface-enhanced Raman scattering (SERS), comprising: a silver substrate having a silver nanostructured surface; and a silver halide passivation layer formed on the surface of the silver substrate. The present disclosure also provides a method for preparing the SERS substrate and a method for SERS trace detection using the substrate.

Description

Technical Field

[0001] This disclosure relates to the field of Raman spectroscopy analysis, and more specifically, to a substrate for trace detection, a method for preparing the substrate, and a method for surface-enhanced Raman scattering trace detection using the substrate. Background Technology

[0002] Noble metals with nanoscale rough surfaces can produce significant surface-enhanced Raman scattering (SERS). Silver (Ag) has a wider range of applications due to its two-order-of-magnitude higher electric field and lower loss than gold (Au), along with its unique surface plasmon properties. However, because metallic silver is prone to oxidation and sulfidation, and its nanoscale surface has high activity, it readily adsorbs various molecules present in the environment. This manifests as difficult-to-label impurity peaks on its blank substrates. The presence of these impurity peaks increases the difficulty of identifying and characterizing the fingerprint peaks of target analytes, severely interfering with the qualitative and quantitative detection of unknown analytes, and even rendering them unusable.

[0003] In realizing the concept disclosed herein, the inventors discovered that how to eliminate impurity peaks using a simple and efficient method without sacrificing sensitivity, in order to obtain better surface-enhanced Raman scattering performance, is a technical problem that urgently needs to be solved in the current field of trace detection. Summary of the Invention

[0004] In view of the above, embodiments of the present disclosure provide a substrate for surface-enhanced Raman scattering, a method for preparing the substrate, and a method for performing surface-enhanced Raman scattering using the substrate.

[0005] According to one aspect of this disclosure, a substrate for surface-enhanced Raman scattering is provided, the substrate comprising: a silver substrate having a silver nanostructured surface; and a silver halide passivation layer formed on the surface of the silver substrate.

[0006] According to embodiments of this disclosure, the silver nanostructure includes at least one of nanorods, nanotubes, nanowires, and nanoparticles.

[0007] According to embodiments of this disclosure, the thickness of the silver halide passivation layer is 1-10 nm.

[0008] According to an embodiment of this disclosure, the thickness of the silver halide passivation layer is 2 nm.

[0009] According to embodiments of this disclosure, the silver halide includes at least one of silver chloride, silver bromide, and silver iodide.

[0010] According to embodiments of this disclosure, the silver halide passivation layer is formed by immersing the silver substrate with a silver nanostructure surface in a modification solution containing halide ions, or by dropping the modification solution containing halide ions onto the silver substrate with a silver nanostructure surface.

[0011] According to another aspect of this disclosure, a method for preparing the above-described substrate for surface-enhanced Raman scattering is provided, comprising: preparing a modification solution containing halide ions using raw materials; and modifying a silver substrate having a silver nanostructure surface using the modification solution.

[0012] According to embodiments of this disclosure, the halide ion includes at least one of chloride ions, bromide ions, and iodide ions.

[0013] According to embodiments of this disclosure, the raw material includes at least one of lithium salt, sodium salt, potassium salt, and acid corresponding to the halide ion.

[0014] According to embodiments of this disclosure, the concentration of halide ions in the modified solution is 0.1-10 mM.

[0015] According to embodiments of this disclosure, the solvent of the modifying liquid is water or alcohol.

[0016] According to embodiments of this disclosure, the alcohol is methanol or ethanol.

[0017] According to embodiments of this disclosure, the modification method used in the step of modifying the silver substrate with a silver nanostructure surface using the modification solution includes: immersing the silver substrate with a silver nanostructure surface in a modification solution containing halide ions; or adding the modification solution containing halide ions dropwise onto the silver substrate with a silver nanostructure surface.

[0018] According to an embodiment of this disclosure, in the step of modifying a silver substrate with a silver nanostructure surface using the modification solution, the modification time is 1-60 min.

[0019] Another aspect of this disclosure provides a method for surface-enhanced Raman scattering, comprising: activating the substrate or the substrate prepared by the above method by illumination; adding a test solution onto the light-activated substrate, or immersing the light-activated substrate in the test solution; and detecting it using a Raman spectrometer.

[0020] According to embodiments of this disclosure, in the step of activating the substrate or the substrate prepared by the above method using light, the light includes at least one of ultraviolet light and visible light.

[0021] According to embodiments of this disclosure, the light activation time is 1-30 minutes.

[0022] According to an embodiment of this disclosure, the wavelength of the ultraviolet light is 365 nm.

[0023] According to embodiments of this disclosure, in the step of detection using a Raman spectrometer, the wavelengths of the Raman spectrometer include 532 nm, 633 nm, 785 nm, and 1064 nm.

[0024] As can be seen from the above technical solutions, the beneficial effects of the substrate, preparation method, and surface-enhanced Raman scattering method provided in this disclosure are as follows:

[0025] 1. By forming a silver halide passivation layer on the surface of a silver nanostructure on a silver substrate and activating the substrate with light before use, the interference of impurity peaks adsorbed on the silver substrate is eliminated, the sensitivity is improved, and the material basis for the quantitative detection of surface-enhanced Raman scattering is laid.

[0026] 2. By forming a silver halide passivation layer on the surface of the silver nanostructure on the silver substrate, the problem of easy oxidation of nano silver is solved, which improves its stability during application and extends its shelf life.

[0027] 3. The preparation process is simple, the cost is extremely low, and it is easy to promote and apply on a large scale. Attached Figure Description

[0028] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0029] Figure 1 A flowchart illustrating the substrate fabrication method in an embodiment of this disclosure is shown schematically.

[0030] Figure 2 A flowchart illustrating the surface-enhanced Raman scattering method in an embodiment of this disclosure is shown schematically.

[0031] Figure 3 The Raman spectrum of a bare silver substrate according to Embodiment 1 of this disclosure is illustrated schematically;

[0032] Figure 4 The Raman spectra of a halide-ion-modified substrate and a bare silver substrate according to Embodiment 1 of this disclosure are illustrated schematically.

[0033] Figure 5(a) schematically shows a transmission electron microscope image of a bare silver substrate according to Embodiment 1 of the present disclosure;

[0034] Figure 5(b) schematically shows a transmission electron microscope image of a halide ion-modified substrate according to Embodiment 1 of the present disclosure;

[0035] Figure 6The Raman spectrum of methylene blue detected on a chloride-modified substrate according to Example 2 of this disclosure is illustrated schematically.

[0036] Figure 7 The Raman spectrum of methylene blue detected on a bromide-modified substrate according to Example 3 of this disclosure is illustrated schematically.

[0037] Figure 8 The Raman spectrum of methylene blue detected on a substrate modified with iodine ions according to Example 4 of this disclosure is illustrated schematically.

[0038] Figure 9 The Raman spectra of methylene blue detected on a bare silver substrate and an iodine-modified substrate according to Comparative Example 1 of this disclosure are schematically shown. Detailed Implementation

[0039] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0041] When using expressions such as "at least one of A, B, or C," it should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, features defined with "first" or "second" may explicitly or implicitly include one or more of the stated features.

[0042] Raman spectroscopy is a molecular-specific fingerprint spectroscopy, and trace substances can be identified and detected using the surface-enhanced Raman scattering (SERS) effect. The SERS mechanism is mainly based on two types of enhancement: physical enhancement and chemical enhancement. Physical enhancement is primarily due to the enhancement of the local electromagnetic field caused by surface plasmon resonance. The type, size, and shape of the metal, as well as the frequency of the incident light, all affect physical enhancement. Silver and gold are the best SERS materials, exhibiting excellent plasmon responses in the visible and near-infrared bands, with Raman signal intensity increased by 5-6 orders of magnitude. Under specific conditions, even single-molecule detection (enhancement factor 10⁻⁶) can be achieved. 14 -10 15 Meanwhile, its small slit width and good spectral shape make it an ultrasensitive analytical tool, which has been widely used in analytical chemistry, especially in trace detection.

[0043] To overcome the drawback of difficult-to-label impurity peaks appearing on blank silver substrates, many researchers have begun to coat the surface of silver nanostructures with an ultrathin protective layer, thereby enabling silver to maintain its metallic activity in oxidizing environments. The main types of protective layers include:

[0044] 1. Coated oxides, such as TiO2, silicon dioxide, aluminum oxide, hafnium oxide, etc.;

[0045] 2. Coated carbon materials, such as glucose hydrolyzed carbon, carbon quantum dots, graphene and graphene oxide, and physically deposited carbon, etc.

[0046] 3. Coated with a dense gold film.

[0047] The advantages of forming a shell coating are: it can eliminate interference from other signals, obtain the signal of the sample itself, and the substrate can be used at higher temperatures. Its disadvantages are: the coating process is relatively complex, and the coating layer often leads to a decrease in Raman sensitivity (by about an order of magnitude). Other methods, such as introducing a passivation layer formed by the self-assembly of alkyl thiols, have the disadvantage of introducing new impurity peaks.

[0048] Therefore, how to obtain better SERS performance by adopting a simple and efficient method to eliminate impurity peaks without sacrificing sensitivity is a technical problem that urgently needs to be solved in the field of trace detection.

[0049] This disclosure provides a substrate for surface-enhanced Raman scattering, the substrate comprising: a silver substrate having a silver nanostructured surface; and a silver halide passivation layer formed on the surface of the silver substrate. The silver substrate is a substrate having a silver nanostructured surface, including but not limited to silver self-supporting substrates or other substrates having a silver nanostructured surface. For example, it can be a pure silver substrate or other types of substrates; any substrate with a silver nanostructured surface can be used, and this disclosure does not limit this.

[0050] It should be noted that the silver nanostructure can be a pure silver nanostructure or a composite nanostructure containing silver, that is, a composite nanostructure containing other elements besides silver; in addition, the surface of the substrate can contain only silver nanostructures or can include composite nanostructures containing silver, as long as the structure of the substrate surface includes silver-containing nanostructures, the embodiments disclosed herein do not limit this.

[0051] In the embodiments of this disclosure, the silver nanostructure includes at least one of nanorods, nanotubes, nanowires and nanoparticles. The silver nanostructure includes, but is not limited to, nanorods, nanotubes, nanowires, nanoparticles and various complex morphologies prepared by physical or chemical methods. It can be applied to any silver-based substrate that is prone to interference from impurity peaks. The embodiments of this disclosure do not limit this.

[0052] In embodiments of this disclosure, the thickness of the silver halide passivation layer is 1-10 nm.

[0053] In embodiments of this disclosure, the thickness of the silver halide passivation layer is 2 nm.

[0054] In the embodiments of this disclosure, the silver halide includes at least one of silver chloride, silver bromide, and silver iodide. Silver halide refers to compounds of silver and halogens. Halogen ions have certain reducing and coordinating properties, which can reduce or displace oxide species adsorbed on the silver-based SERS substrate. Furthermore, they readily form ionic compounds with very low solubility with silver ions, achieving the desorption of surface impurity molecules and forming a passivation layer to prevent further adsorption of environmentally interfering molecules. Simultaneously, by forming a protective film on the silver substrate, the shelf life of the substrate is extended. In addition, during use, since halogen ions lack Raman activity and silver halide easily decomposes under ultraviolet and visible light, a fresh surface is formed on the substrate. This fresh surface readily adsorbs the target molecules to be measured, improving detection sensitivity.

[0055] In embodiments of this disclosure, the silver halide passivation layer is formed by immersing the silver substrate with the silver nanostructure surface in a modification solution containing halide ions, or by dropping the modification solution containing halide ions onto the silver substrate with the silver nanostructure surface.

[0056] Figure 1 A flowchart illustrating the substrate fabrication method in an embodiment of this disclosure is shown.

[0057] The embodiments of this disclosure provide a method for preparing the above-described substrate for surface-enhanced Raman scattering, namely a surface modification method, such as... Figure 1 As shown, it includes:

[0058] Step S1: Prepare a modified solution containing halide ions using the raw materials;

[0059] Step S2: Modify the silver substrate with a silver nanostructure surface using the modification solution.

[0060] In embodiments of this disclosure, the halide ions include at least one of chloride ions, bromide ions, and iodide ions.

[0061] In the embodiments of this disclosure, the raw materials include at least one of lithium salt, sodium salt, potassium salt and acid corresponding to the halide ions. Any solution containing halide ions can be used, and the embodiments of this disclosure do not limit this.

[0062] In the embodiments of this disclosure, the concentration of halide ions in the modified solution is 0.1-10 mM.

[0063] In the embodiments of this disclosure, the solvent of the modification solution is water or alcohol. After the substrate is prepared, it needs to be dried before use. Due to the large surface area of ​​the nanostructure, using a volatile and easily dried solvent is more beneficial for subsequent operations. Optionally, easily volatile methanol and ethanol can be used.

[0064] In the embodiments of this disclosure, the alcohol is methanol or ethanol.

[0065] In the embodiments of this disclosure, the step of modifying the silver substrate with a silver nanostructure surface using the modifying solution includes the following modification methods: immersing the silver substrate with a silver nanostructure surface in a modifying solution containing halide ions; or dropwise adding the modifying solution containing halide ions onto the silver substrate with a silver nanostructure surface. Any method that allows the modifying solution to contact and react with the substrate surface to form a silver halide passivation layer can be used, and the embodiments of this disclosure are not limited to this.

[0066] In the embodiments of this disclosure, the modification time for the silver substrate with a silver nanostructure surface using the modification liquid is 1-60 min.

[0067] It should be noted that the following factors were considered when designing the modification time and the thickness of the silver halide passivation layer: If the modification time is too short, there will not be enough time to form a silver halide passivation layer, or the formed silver halide passivation layer will be too thin, failing to effectively eliminate impurity peaks. If the modification time is too long, the resulting silver halide passivation layer will be too thick, reducing the surface-enhanced Raman scattering effect and hindering subsequent photoactivation. A modification time of 1-60 minutes can correspond to a silver halide passivation layer thickness of 1-10 nm. This thickness of silver halide passivation layer has a good surface-enhanced Raman scattering effect and also facilitates photoactivation.

[0068] Figure 2 A flowchart illustrating the surface-enhanced Raman scattering method in an embodiment of this disclosure is shown schematically.

[0069] Embodiments of this disclosure provide a method for detecting trace amounts of surface-enhanced Raman scattering, such as... Figure 2 As shown, it includes:

[0070] Step S3: Activate the substrate or the substrate prepared by the above method using light;

[0071] Step S4: Add the test solution to the photoactivated substrate, or immerse the photoactivated substrate in the test solution;

[0072] Step S5: Detect using a Raman spectrometer.

[0073] In the embodiments of this disclosure, the step of activating the substrate or the substrate prepared by the above method using light irradiation includes at least one of ultraviolet light and visible light. It should be noted that since the silver halide passivation layer can decompose under visible light, it needs to be stored in the dark. To accelerate the decomposition of the silver halide passivation layer, ultraviolet light irradiation can be used to decompose it back into a silver active substrate with SERS effect, thus enabling normal Raman detection. Furthermore, since the substrate only needs to be activated by light during use, the shelf life of the substrate is extended, allowing the substrate with the silver halide passivation layer to be stored for more than six months.

[0074] In embodiments of this disclosure, the light activation time is 1-30 minutes.

[0075] In embodiments of this disclosure, the wavelength of the ultraviolet light is 365 nm.

[0076] In the embodiments of this disclosure, the wavelength of the Raman spectrometer used for detection includes 532 nm, 633 nm, 785 nm and 1064 nm.

[0077] The embodiments of this disclosure modify a silver substrate with a silver nanostructure surface to achieve the desorption of surface impurity molecules and the formation of a silver halide passivation layer to prevent further adsorption of environmental interference molecules. When the substrate is used for detection, the silver halide passivation layer decomposes upon light exposure, and the fresh substrate effectively increases sensitivity. The silver halide passivation layer obtained through modification in the embodiments of this disclosure effectively eliminates interference from impurity peaks adsorbed on the silver substrate, improves sensitivity, and lays the material basis for quantitative detection by surface Raman enhancement. Simultaneously, it solves the problem of easy oxidation of nano-silver, improves its stability during application, and is beneficial for the long-term preservation of silver SERS substrates. Furthermore, it has the advantages of simple preparation process, strong practicality, and the ability to perform quantitative detection.

[0078] The substrate of the present disclosure will be described in detail below with reference to the embodiments and related experiments.

[0079] Example 1

[0080] After preparation, ordinary silver-based SERS substrates will exhibit significant impurity peaks when exposed to air (usually after 3 hours) without special protection, severely affecting subsequent Raman tests. Therefore, a modification method is needed to remove these impurity peaks. First, a bare silver substrate blank sample before modification was subjected to Raman testing using an ATR8300 micro Raman spectrometer (Xiamen, China). The test parameters were: integration time 2 s, laser power 100 mW, and laser wavelength 785 nm.

[0081] The Raman spectrum of the unmodified bare silver substrate was measured as follows: Figure 3 As shown, at 382cm -1 857cm -1 1131cm -1 1404cm -1 and 1606cm -1 There are obvious clutter peaks nearby, accompanied by several weaker clutter peaks (such as 2139 cm⁻¹). -1 The attribution of these impurity peaks is difficult to determine accurately, possibly due to different forms of oxygen adsorbed on the silver surface. For some low-concentration substances, the presence of impurity peaks can interfere with the characteristic peaks of some analytes, making substance identification difficult. Therefore, we modified the silver substrate with impurity peaks according to the following steps:

[0082] (1) Prepare a 1 mM aqueous solution containing chloride, bromide and iodide ions. To compare the effects of different halide ions and their forms on the modification effect, the effects of KCl, HCl, KBr, LiBr, NaI and KI were investigated respectively. Since the solution preparation method is common knowledge in the industry, it will not be described in detail here.

[0083] (2) Immerse the silver-based SERS substrate with impurity peaks in a solution of the above ions at a concentration of 1 mM. After 30 min, take it out, gently blow away the surface solution with a rubber bulb, and air dry and store it in the dark.

[0084] (3) Remove the substrate and irradiate it with a 5W 365nm wavelength ultraviolet lamp for 5 minutes, and then perform Raman testing. The instrument model and parameters are the same as above.

[0085] Test results are as follows Figure 4 As shown, compared with the original impurity peaks, the substrate modified with halide ions no longer exhibits obvious Raman peaks, indicating that the modification method can eliminate impurity peaks. The transmission electron microscope (TEM) image of the bare silver substrate is shown in Figure 5(a), and the TEM image of the substrate modified with iodine ions is shown in Figure 5(b). It can be seen that the surface of the silver nanorods on the bare silver substrate before modification has an adsorption layer of 1-2 nanometers, which has poor crystallinity and is difficult to characterize its phase; the surface of the silver nanorods on the modified substrate forms a passivation layer of about 2 nanometers, which has good crystallinity and clearly shows ordered lattice fringes.

[0086] Example 2

[0087] To verify the Raman enhancement effect of chloride ion-modified silver substrates, methylene blue (MB) was used as the detector molecule for detection and evaluation. Silver substrates containing impurity peaks were immersed in a 10 mM KCl aqueous solution, ensuring the solution level covered the substrate surface. After 10 min, the substrates were removed, and the surface modification solution was gently dried with a syringe rubber bulb. The substrates were then activated with a 365 nm UV lamp for 1 min, followed by immersion in MB standard solutions with concentrations ranging from 0.1 ppb (μg / L) to 1 ppm (mg / L) for 5 minutes. The substrates were then removed, gently dried with a syringe rubber bulb, and any remaining solution was absorbed with filter paper before being placed on a Raman spectrometer for detection. Test parameters: integration time 1 s, integration times 1, laser power 400 mW, laser wavelength 532 nm.

[0088] Test results are as follows Figure 6 As shown, from Figure 6 As can be seen, the Raman spectrum (curve 1) of the substrate modified with chloride ions for detecting MB shows that all peaks are characteristic peaks of the detected substance. As the detection concentration decreases, the intensity of different characteristic peaks decreases (curve 2), and the intensity change has a good linear relationship with the concentration. Under the conditions of this embodiment, the modified substrate can clearly detect MB molecules at concentrations below 0.01 ppm (curve 3), demonstrating the characteristics of ultra-trace analysis, and no interference from the modification background is observed (curves 4 and 5).

[0089] Example 3

[0090] To verify the Raman enhancement effect of bromide-corrected silver substrates, silver-based SERS substrates prepared and stored in air for half a month were immersed in a 1 mM KBr aqueous solution, with the liquid level completely covering the silver substrate surface. After immersion for 30 minutes, the substrates were removed, allowed to air dry naturally, and stored away from light. One month later, the substrates were activated with a 365 nm UV lamp for 2 minutes, and then detected and evaluated using methylene blue (MB) as the detector molecule. 30 μL of MB standard solutions of different concentrations were added dropwise to the surface of a 5 mm x 5 mm substrate. After approximately 30 seconds, the surface test solution was blown away with a bulb syringe, and any remaining solution was absorbed with filter paper. The substrate was then placed on a Raman spectrometer for detection. Test parameters: integration time 1 s, integration times 1, laser power 400 mW, laser wavelength 633 nm.

[0091] Test results are as follows Figure 7 As shown, from Figure 7 As can be seen, the Raman spectrum (curve 1) of the bromide-modified substrate for detecting MB shows that all peaks are characteristic peaks of the detected substance. As the detection concentration decreases, the intensity of different characteristic peaks decreases (curve 2), and the intensity change has a good linear relationship with the concentration. Under the conditions of this embodiment, the modified substrate, after being stored for one month, can clearly detect MB molecules at concentrations below 0.01 ppm (curve 3), demonstrating the characteristics of ultra-trace analysis, without interference from the modification background (curves 4 and 5).

[0092] Example 4

[0093] To verify the Raman enhancement effect of the iodine-modified substrate, a silver-based SERS substrate prepared and stored in air for 3 months was immersed in a 1 mM KI ethanol solution, ensuring the liquid level completely covered the substrate surface. After immersion for 60 minutes, the substrate was removed, allowed to air dry naturally, and stored away from light. Six months later, the substrate was activated with a 365 nm UV lamp for 10 minutes, and then detected and evaluated using methylene blue (MB) as the detector molecule. 30 μL of MB standard solutions of different concentrations were dropped onto the surface of a 5 mm x 5 mm substrate. After approximately 60 seconds, any unevaporated solution was dried with a syringe rubber bulb before detection on a Raman spectrometer. Test parameters: integration time 1 s, integration times 1, laser power 400 mW, laser wavelength 785 nm.

[0094] Test results are as follows Figure 8 As shown, from Figure 8As can be seen, the Raman spectrum (curve 1) of the silver substrate modified with iodine ions for detecting MB shows that all peaks are characteristic peaks of the detected substance. As the detection concentration decreases, the intensity of different characteristic peaks decreases, and the intensity change has a good linear relationship with the concentration. Under the conditions of this embodiment, the substrate, after modification and storage for 6 months, can clearly detect MB molecules at concentrations below 1 ppb (curve 4), demonstrating the characteristics of ultra-trace analysis, without interference from the modification background (curve 4).

[0095] Comparative Example 1

[0096] After preparation, ordinary silver-based SERS substrates will show obvious impurity peaks when left in the air for a period of time. Two substrates prepared under the same conditions and stored for one week were taken out. One substrate was chemically modified, while the other was left untreated. The methylene blue dye molecules of the two substrates were detected, and the changes in the Raman spectrum peak positions and peak shapes were compared and analyzed.

[0097] The prepared silver-based SERS substrate was immersed in a 1 mM KI aqueous solution for 1 hour, then removed and allowed to air dry naturally to obtain an iodine-modified substrate. 30 μL of a methylene blue standard aqueous solution (1 ppm) was added to the surface of both the iodine-modified and unmodified substrates (5 mm x 5 mm). After addition, the substrates were allowed to stand for 5 minutes, the surface was dried with a syringe rubber bulb, and any remaining solution around the substrate was absorbed with filter paper. The substrates were then analyzed using a Raman spectrometer. The integration time was 0.8 s, the laser power was 50 mW, and the laser wavelength was 785 nm.

[0098] The test results are as follows Figure 9 As shown, the methylene blue Raman peak is most pronounced at 1 ppm, and is highest at 450 cm⁻¹. -1 499cm -1 768cm -1 1182cm -1 1393cm -1 and 1622cm -1 Obvious signals were measured at multiple locations. The substrate modified with iodine ions completely removed impurity peaks (curve 3), and the peaks generated after immersion in MB were all vibrational peaks of different groups of MB (curve 1). In contrast, the unmodified substrate still exhibited its peak shape after immersion in MB (curves 2 and 4). The peak at 1606 cm⁻¹ was particularly prominent. -1 The impurity peak and the side peak of MB at 1622 cm⁻¹ -1The peaks are very close and difficult to distinguish (curve 2). The intensity and sharpness of the MB peak on the substrate containing impurity peaks are significantly lower than those on the modified substrate. It is foreseeable that impurity peaks on SERS substrates will seriously affect the detection of target molecules, especially for the detection of unknown molecules in complex systems. The presence of impurity peaks seriously interferes with the identification of substances, and the decrease in sensitivity makes trace and ultra-trace quantitative analysis difficult to achieve.

[0099] As can be seen from the above embodiments and comparative examples, the preparation method provided by the present invention is simple, has a significant effect on eliminating impurity peaks, exhibits high sensitivity, and demonstrates a remarkable surface enhancement effect on the substrate, enabling quantitative analysis of trace substances. Furthermore, the method provided by the present invention significantly improves the stability and durability of SERS substrates, possessing high practicality and broad application prospects in food, environment, biology, and medicine.

[0100] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0101] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A method for surface-enhanced Raman scattering, characterized in that, include: Activating a substrate for surface-enhanced Raman scattering using light illumination; The test solution is dropped onto the light-activated substrate, or the light-activated substrate is immersed in the test solution; as well as Detection was performed using a Raman spectrometer. The substrate includes: A silver substrate having a silver nanostructure surface, wherein the silver nanostructure includes a pure silver structure or a composite nanostructure containing silver; and a silver halide passivation layer formed on the surface of the silver substrate, wherein the silver halide passivation layer reduces or replaces oxides adsorbed on the surface of the silver substrate to prevent the adsorption of environmentally interfering molecules; the silver halide passivation layer decomposes into a fresh surface under ultraviolet and / or visible light, and the fresh surface has an enhanced adsorption capacity for the target molecules to be tested.

2. The method according to claim 1, characterized in that, In the step of activating the substrate for surface-enhanced Raman scattering using light, the light includes at least one of ultraviolet light and visible light.

3. The method according to claim 2, characterized in that, The light activation time is 1-30 minutes.

4. The method according to claim 3, characterized in that The wavelength of the ultraviolet light is 365nm.

5. The method according to claim 4, characterized in that, In the step of detection using a Raman spectrometer, the wavelengths of the Raman spectrometer include 532nm, 633nm, 785nm, and 1064nm.

6. The method according to claim 1, characterized in that, The silver nanostructure includes at least one of nanorods, nanotubes, nanowires, and nanoparticles.

7. The method according to claim 1, characterized in that, The thickness of the silver halide passivation layer is 1-10 nm.

8. The method according to claim 7, characterized in that, The thickness of the silver halide passivation layer is 2 nm.

9. The method according to claim 7, characterized in that, The silver halide includes at least one of silver chloride, silver bromide, and silver iodide.

10. The method according to claim 1, characterized in that The silver halide passivation layer is formed by immersing the silver substrate with the silver nanostructure surface in a modification solution containing halide ions, or by dropping the modification solution containing halide ions onto the silver substrate with the silver nanostructure surface.

11. The method according to any one of claims 6 to 10, characterized in that, The method further includes the preparation of the substrate, specifically including: Prepare a modified solution containing halide ions using raw materials; and The modified liquid was used to modify a silver substrate with a silver nanostructure surface.

12. The method according to claim 11, characterized in that, The halide ions include at least one of chloride ions, bromide ions, and iodide ions.

13. The method according to claim 12, characterized in that, The raw materials include at least one of lithium salt, sodium salt, potassium salt and acid corresponding to the halide ion.

14. The method according to claim 13, characterized in that, The concentration of halide ions in the modified solution is 0.1-10 mM.

15. The method according to claim 14, characterized in that, The solvent for the modification solution is water or alcohol.

16. The method according to claim 15, characterized in that, The alcohol is methanol or ethanol.

17. The method according to claim 11, characterized in that, The modification method used in the step of modifying the silver substrate with the silver nanostructure surface using the modification solution includes: The silver substrate with the silver nanostructured surface is immersed in a modification solution containing halide ions; or The halogen-containing modified liquid was dropleted onto the silver substrate with the silver nanostructure surface.

18. The method according to claim 17, characterized in that, In the step of modifying the silver substrate with a silver nanostructure surface using the modification solution, the modification time is 1-60 min.

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