Surface-enhanced Raman detection method based on laser-induced deposition

Abstract

The invention discloses a surface-enhanced Raman detection method based on laser-induced deposition, and belongs to the technical field of micro-nano particle deposition and detection. According to the method disclosed by the invention, the gold nanoparticles and the to-be-detected particles are driven to be enriched and precisely deposited to a target area by utilizing laser local heating, and Raman detection is synchronously carried out, so that high-sensitivity detection on trace substances is realized. According to the method, the problems of uneven particle deposition, uncontrollable signal enhancement and the like in the traditional surface enhanced Raman scattering substrate preparation are solved, meanwhile, the requirement of an extra laser source in a traditional detection method is avoided, and integration of laser deposition and detection is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano particle deposition and detection, and particularly to a surface-enhanced Raman detection method based on laser-induced deposition. Background Art

[0002] Surface-Enhanced Raman Scattering (SERS) is a highly sensitive spectroscopic detection technique that can significantly enhance the intensity of the Raman scattering signal of molecules. This technique relies on the plasmon resonance effect of metal nanoparticles, and through the local electric field enhancement effect, the analyte molecules can still be efficiently detected at low concentrations. Therefore, SERS has been widely applied in the fields of biological detection, environmental monitoring, food safety, and drug analysis. However, the signal enhancement effect of SERS highly depends on the distribution and aggregation state of metal nanoparticles. How to accurately deposit nanoparticles in a specific area and effectively improve the detection sensitivity remains an important research topic.

[0003] Currently, common methods for preparing SERS substrates include self-assembly deposition, electrochemical deposition, and solvent evaporation-induced deposition, etc. Among them, the droplet evaporation-induced deposition method has attracted attention due to its simplicity. However, this method is easily affected by the "coffee ring effect", resulting in the nanoparticles mainly aggregating at the droplet edge, leading to uneven distribution of SERS active hotspots and affecting the stability of the detection signal. To overcome this problem, some studies have used electric or magnetic fields to control the internal flow of droplets to optimize the deposition distribution of nanoparticles. However, these methods usually require additional electrode designs or external field sources, increasing the experimental complexity.

[0004] On the other hand, Raman detection usually requires laser excitation, and the detection area often needs to undergo complex pre-treatments (spin coating, laser bubble induction, magnetron sputtering, etc.) to obtain high-sensitivity signals. How to directly optimize the SERS substrate during the nanoparticle deposition process and synchronously complete Raman detection is an important challenge faced by the current development of SERS technology. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a surface-enhanced Raman detection method based on laser-induced deposition with simple steps, high detection efficiency, good signal stability and repeatability, including the following steps: (1) Prepare a mixed dispersion of gold nanoparticles and analyte particles; (2) Drop the mixed dispersion onto the substrate surface, and use a single continuous laser source for laser irradiation to form a thermal Marangoni convection, induce droplet evaporation and Raman signal excitation, and synchronously perform deposition and detection; (3) Regulate the deposition morphology of gold nanoparticles and the particles to be measured, and optimize the uniformity and enhancement effect of surface-enhanced Raman scattering signals; (4) Wait for the droplet to completely evaporate, and the gold nanoparticles and the particles to be measured are co-deposited at the center of laser irradiation; (5) According to the feedback of the Raman scattering signal obtained in real time, adjust the parameters of the laser source to optimize the enhancement effect of the surface-enhanced Raman scattering signal; analyze the Raman spectroscopy detection information, characterize the molecular information of the particles to be measured, and complete qualitative and quantitative analysis.

[0006] Preferably, in the step (1), the particle size of the gold nanoparticles is 10 - 100 nm.

[0007] Preferably, in the step (1), the particle size of the particles to be measured is 1 - 10 μm.

[0008] Preferably, in the step (1), a solution system with low affinity for both gold nanoparticles and the particles to be measured is selected to prepare the mixed dispersion.

[0009] More preferably, the poor solvents of gold nanoparticles and the particles to be measured are used to prepare the mixed dispersion; the poor solvents include at least one of deionized water, ethanol, isopropanol, and acetone.

[0010] Preferably, in the step (1), the concentration of the gold nanoparticles is 0.01 - 0.1 mg / mL.

[0011] Preferably, in the step (1), the concentration of the particles to be measured is 0.001 - 0.5 mg / mL.

[0012] Based on the above preferred solutions, according to the chemical properties of the analyte and the stability of the particles, a suitable dispersion solvent is selected, such as a solution system with low affinity (i.e., poor solvent) for both gold and the particles to be measured, which is beneficial to the migration and deposition of the particles towards the laser center during evaporation. Commonly used solvents include but are not limited to deionized water, ethanol, isopropanol, acetone, and their mixtures. Among them, ethanol and isopropanol are suitable for hydrophobic particles, while deionized water is suitable for hydrophilic particles. In actual operation, after mixing the above two types of particles and dispersing them by ultrasonic or other suitable methods, a stable mixed droplet containing gold nanoparticles and the particles to be measured can be formed.

[0013] Preferably, in the step (2), the power density of the laser irradiation is 0.1 - 2.0 mW / μm 2 ; the spot diameter is 1 - 10 μm; the irradiation time is 10 - 300 s.

[0014] In the context of the method of surface-enhanced Raman scattering, when the present invention uses a single continuous laser source with a wavelength resonant with gold nanoparticles for irradiation, the laser source has the ability to simultaneously induce droplet evaporation and excite Raman signals. The above-mentioned preferred parameters can be adjusted according to the particle concentration and the sample response sensitivity. During the laser irradiation process, the photothermal effect causes a local temperature rise, resulting in the formation of Marangoni flow inside the droplet, promoting the aggregation of gold nanoparticles under the action of the laser and driving the particles to be measured to deposit together towards the center of the light spot, forming a high-density SERS active region. At the same time, the localized surface plasmon resonance (LSPR) effect generated by the gold nanoparticles significantly enhances the Raman scattering signal of the molecule to be measured, realizing synchronous deposition and detection.

[0015] Preferably, in the step (3), the method of regulating the deposition morphology of the gold nanoparticles and the particles to be measured includes adjusting the laser power, the spot radius, and the solution physical properties of the mixed dispersion liquid.

[0016] By adjusting the laser power, the spot radius, and the physical properties of the solution (such as surface tension, viscosity, evaporation rate, etc.), precise regulation of the deposition morphology of the gold nanoparticles and the particles to be measured can be achieved, thereby improving the uniformity and enhancement effect of the SERS signal. Specifically, the laser power (0.1~2.0 mW / μm 2 ) determines the local heating intensity, thus affecting the velocity of the Marangoni flow and the aggregation rate of the particles. Too low power may not be sufficient to drive effective convection, resulting in non-concentrated particle deposition; too high power may cause droplet splashing or local solvent boiling, forming irregular deposition. The spot radius (1~10 μm) affects the spatial scale of the aggregation region. A smaller spot is conducive to forming a high-density deposition region, thereby enhancing the local Raman signal, but may limit the participation of the particles to be measured; a larger spot is conducive to covering more particles, but the deposition density may decrease. In terms of the solution physical properties, selecting a solvent with moderate surface tension and suitable volatility (such as a mixed system of ethanol, propanol, and water) helps to regulate the evaporation rate and the interfacial flow field, suppress the coffee ring effect, and promote the aggregation of particles towards the laser center; if a solvent with high viscosity or extremely low volatility is used, it may lead to lagging particle deposition and poor aggregation dispersibility.

[0017] When the droplet is completely evaporated, the gold nanoparticles and the particles to be measured can be co-deposited at the center of the laser irradiation. During this process, the localized surface plasmon resonance effect generated between the laser and the gold particles significantly enhances the Raman signal, enabling high-efficiency detection even when the concentration of the molecule to be measured is relatively low. By analyzing parameters such as the characteristic peak intensity, full width at half maximum, and peak position drift of the Raman spectrum, the structural information of the molecule to be measured can be accurately characterized, thereby realizing high-sensitivity qualitative and quantitative analysis.

[0018] Preferably, in the step (5), the criteria for optimizing the surface-enhanced Raman scattering signal enhancement effect include maximizing the Raman signal intensity, improving the signal-to-noise ratio, and the consistency of spectral peak positions and full widths at half maximum.

[0019] According to the Raman signal feedback obtained in real time, parameters such as laser power, irradiation time, and laser radius are adjusted to optimize the SERS signal enhancement effect. The optimization criteria include but are not limited to maximizing the Raman signal intensity, improving the signal-to-noise ratio, and the consistency of spectral peak positions and full widths at half maximum, thereby ensuring the sensitivity, repeatability, and reliability of the detection process. On this basis, combined with the characteristic peak positions, relative intensities, and full width at half maximum changes of the molecules to be detected in the Raman spectral data, the analysis of molecular structure information is realized. This step can be used to further identify the characteristic differences between different molecules and achieve efficient, accurate identification and qualitative detection of trace analytes.

[0020] Based on the above technical solutions, the design concept and principle of the present invention are as follows: The present invention uses laser local heating to induce droplet evaporation, drive the enrichment of gold nanoparticles and analyte particles, and precisely deposit them onto the target area and simultaneously perform Raman detection, realizing in-situ highly sensitive detection of trace substances.

[0021] By using a single laser source to synchronously complete deposition and detection, the separation operation of laser-induced deposition and Raman detection in traditional SERS research is avoided, improving the detection efficiency and spatial resolution. By laser regulating the internal heat flow and optical force in the droplet, gold nanoparticles and analyte particles are enriched in the illumination center area, and the deposition of nanoparticles is precisely controlled, thereby forming a highly uniform SERS substrate. During the deposition process, the surface plasmon resonance effect of gold nanoparticles enhances the local electric field, enabling the real-time synchronous enhancement of the Raman scattering signal of the analyte molecules without additional signal amplification steps. The detection limit is improved, thereby realizing the precise analysis of trace substances.

[0022] Therefore, this method overcomes the problems of uneven particle deposition and uncontrollable signal enhancement in the preparation of traditional SERS substrates, and at the same time avoids the need for an additional laser source in traditional detection methods, realizing the integrated integration of laser deposition and detection.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The invention uses a single laser source to simultaneously induce particle deposition and enhance the Raman signal, realizing the "one-step" construction and detection of SERS substrates, greatly simplifying the experimental process and improving the detection efficiency.

[0024] 2. By inducing the evaporation of liquid droplets with a laser, the movement of nanoparticles is regulated using local heat flow and optical forces, enabling the precise enrichment of gold nanoparticles and the particles to be measured in the laser irradiation area, avoiding the uneven distribution of particles caused by the "coffee ring effect", ensuring the stability of SERS active hotspots, and improving signal repeatability.

[0025] 3. Since the laser induces the deposition of gold nanoparticles into a high-density area, a local surface plasmon coupling effect is formed, significantly enhancing the electromagnetic field, thereby enhancing the Raman signal intensity. It can precisely enrich the particles to be measured within the micro-nano scale range, enabling the efficient detection of the analyte even at low concentrations, improving the detection limit. It is suitable for the detection of trace substances and has broad application prospects in the fields of biosensing, environmental monitoring, food safety, and pharmaceutical analysis.

[0026] 4. During the deposition process, the Raman signal can be monitored in real time, and the laser parameters are optimized according to the signal feedback to achieve dynamic adjustment, improving the accuracy and controllability of SERS substrate preparation.

[0027] 5. The traditional methods for constructing SERS substrates rely on templates, chemical modification, or external electric fields, which limit the scope of application. The present invention uses laser non-contact regulation, without the need for additional templates or external electric fields, and is applicable to different types of substrate materials, including glass, silicon wafers, and flexible substrates, broadening the application scenarios. Description of the Drawings

[0028] Figure 1 is the optical path diagram of surface-enhanced Raman detection based on laser-induced deposition; In the figure, 1: Raman detection device; 2: mirror; 3: X50 objective lens / X20 objective lens; 4: silicon substrate / silica substrate; 5: continuous detection laser; 6: resonance laser matching the nanoparticles; Figure 2 is the flow chart of the surface-enhanced Raman detection method based on laser-induced deposition; Figure 3 is the microscope image of gold nanoparticles and the sample to be measured deposited at the laser center after the evaporation of the substrate liquid droplet induced by the laser; Figure 4 is the Raman spectrum diagram of the surface-enhanced Raman detection method based on laser-induced deposition and the control group. Detailed Embodiments

[0029] The present invention will be further illustrated below by way of examples, but the present invention is not limited to the scope of the examples described herein. The experimental methods without specific conditions noted in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0030] In the following examples: Adopt as Figure 1Perform surface-enhanced Raman detection based on laser-induced deposition on the optical path shown. A single laser source is used, where the laser is both used to induce droplet evaporation and nanoparticle deposition and can directly excite Raman signals to achieve highly sensitive detection of the particles to be measured.

[0031] In the experimental setup for implementing the above optical path, the plasmon-exciting laser (532 nm is selected in this experiment) acts on the droplet after being focused by a lens, generating thermo-Marangoni convection and optical forces inside the droplet to drive gold nanoparticles and the particles to be measured to concentrate towards the laser center. At the same time, a local high electric field is formed in the laser irradiation area to enhance Raman signals, enabling the detection of the molecular information of the particles to be measured.

[0032] Example 1 This example provides a surface-enhanced Raman detection method based on laser-induced deposition, as Figure 2 shown, the steps are as follows: (1) Select an appropriate substrate (silicon substrate) and perform hydrophilic treatment to improve the spreading property of the droplet; prepare a gold nanoparticle solution and a dispersion of the particles to be measured, and mix them to form a mixed dispersion; among them, the solvent of the mixed dispersion is deionized water, the particle size of the gold nanoparticles is 50 nm, and the concentration is 0.05 mg / mL; the particles to be measured are polystyrene, the particle size is 5 μm, and the concentration is 0.01 mg / mL; (2) Drop the mixed dispersion on the substrate and irradiate it with a single continuous laser source, while inducing droplet evaporation and exciting Raman signals; during the laser irradiation process, due to the action of thermo-Marangoni convection and optical forces inside the droplet, the gold nanoparticles and the particles to be measured gather towards the laser center, and deposition and detection are carried out synchronously; (3) By adjusting the laser power, spot radius, and physical properties of the solution (including surface tension, viscosity, evaporation rate, etc.), achieve precise control of the deposition morphology of the gold nanoparticles and the particles to be measured, and further improve the uniformity and enhancement effect of the SERS signal; (4) As the droplet completely evaporates, the nanoparticles are finally deposited in the laser action area, forming a high-density SERS substrate, and using the local surface plasmon resonance effect generated between the laser and the gold particles to enhance Raman signals; (5) According to the feedback of the Raman signals obtained in real time, adjust parameters such as laser power, irradiation time, and laser radius to make the deposition process more precisely controllable, improve the uniformity of the SERS substrate and the signal enhancement effect; combine the characteristic peak positions, relative intensities, and full width at half maximum changes of the molecules to be measured in the Raman spectrum data to complete the analysis of the molecular structure information.

[0033] Example 2 This embodiment specifically shows the deposition CCD images of the particles to be measured and gold nanoparticles after the evaporation of the gold nanoparticle-containing solution induced by laser during the detection process of Embodiment 1. The results are as Figure 3 shown.

[0034] It can be Figure 3 observed that highly enriched nanostructures are formed in the laser action area, effectively curbing the "coffee ring" phenomenon and providing an efficient hot spot distribution for surface-enhanced Raman detection.

[0035] Embodiment 3 In this embodiment, a dispersion of particles to be measured without gold nanoparticles under the same conditions is used as a control group. The Raman peak intensities of the particle deposition after the natural evaporation of the droplet and the particle deposition after the evaporation of the gold nanoparticle-containing solution induced by laser in Embodiment 1 are tested and compared. The results are as Figure 4 shown.

[0036] Figure 4 The Raman spectra of the particles to be measured detected by the technology of the present invention are shown, indicating that this method can effectively enhance the Raman signal (this method is more than 4 times higher than natural evaporation), improving the detection sensitivity. This method utilizes the Marangoni effect to complete the co-precipitation of nanoparticles and the particles to be measured, realizing the integrated Raman measurement and the preparation of SERS.

[0037] During the test, due to the surface plasmon resonance effect of gold nanoparticles, the local electric field in the laser action area is greatly enhanced, improving the Raman scattering signal. By adjusting parameters such as laser power and laser spot, the distribution state of gold nanoparticles can be optimized, further enhancing the SERS activity. During the particle deposition process, the Raman detector can obtain information such as the peak value, full width at half maximum, and intensity of the Raman spectrum in real time, so as to characterize the molecular structure of the particles to be measured. According to the Raman signal feedback, the laser parameters can be dynamically adjusted to make the deposition process more accurate and controllable, improving the uniformity of the SERS substrate and the signal enhancement effect.

[0038] During the deposition process, gold nanoparticles form a surface plasmon coupling effect, generating a strong local electric field, thereby enhancing the Raman scattering signal of the particles to be measured. In addition, the thermal effect of the laser further optimizes the enrichment state of the particles, making the particles to be measured concentrate in the SERS active area, significantly improving the detection sensitivity.

[0039] In summary, the surface-enhanced Raman detection method based on laser-induced deposition of the present invention uses a single laser source to simultaneously induce droplet evaporation, drive the precise deposition of gold nanoparticles and the particles to be measured, and enhance the Raman signal, realizing in-situ high-sensitivity detection of target molecules. Compared with the traditional SERS substrate preparation and detection methods, the present invention uses a single laser source to synchronously complete deposition and detection, avoiding the separate operations of laser-induced deposition and Raman detection in traditional SERS research, and improving the detection efficiency and spatial resolution. In addition, the deposition of nanoparticles is precisely controlled. By laser regulating the internal heat flow and optical force in the droplet, the gold nanoparticles and the particles to be measured are enriched in the central area of the light illumination, thus forming a highly uniform SERS substrate. Moreover, during the deposition process, the surface plasmon resonance effect of the gold nanoparticles enhances the local electric field, synchronously enhancing the Raman scattering signal of the molecules to be measured without additional signal amplification steps, improving the detection limit and realizing precise analysis of trace substances. This method has broad application prospects in the fields of biosensing, environmental monitoring, food safety, and pharmaceutical analysis.

[0040] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A surface-enhanced Raman detection method based on laser-induced deposition, characterized in that It includes the following steps: (1) Prepare a mixed dispersion of gold nanoparticles and the particles to be measured; (2) Drop the mixed dispersion onto the surface of the substrate, and irradiate it with a single continuous laser source to form thermo-Marangoni convection, induce droplet evaporation and Raman signal excitation, and perform deposition and detection synchronously; (3) Regulate the deposition morphology of gold nanoparticles and the particles to be measured, and optimize the uniformity and enhancement effect of the surface-enhanced Raman scattering signal; (4) Wait for the droplet to completely evaporate, and gold nanoparticles and the particles to be measured are co-deposited at the center of the laser irradiation; (5) According to the feedback of the Raman scattering signal obtained in real time, adjust the parameters of the laser source to optimize the enhancement effect of the surface-enhanced Raman scattering signal; analyze the Raman spectrum detection information, characterize the molecular information of the particles to be measured, and complete qualitative and quantitative analysis.

2. The surface enhanced Raman detection method based on laser induced deposition according to claim 1, characterized in that: In the step (1), the particle size of the gold nanoparticles is 10 - 100 nm.

3. The surface-enhanced Raman detection method based on laser-induced deposition according to claim 1, characterized in that: In the step (1), the particle size of the particles to be measured is 1 - 10 μm.

4. The surface enhanced Raman detection method based on laser induced deposition according to claim 1, characterized in that: In the step (1), a solution system with low affinity for both gold nanoparticles and the particles to be measured is selected to prepare the mixed dispersion.

5. The surface-enhanced Raman detection method based on laser-induced deposition according to claim 4, wherein: The mixed dispersion is prepared with a poor solvent for gold nanoparticles and the particles to be measured; the poor solvent includes at least one of deionized water, ethanol, isopropanol, and acetone.

6. The surface-enhanced Raman detection method based on laser-induced deposition according to claim 1, wherein: In the step (1), the concentration of the gold nanoparticles is 0.01 - 0.1 mg / mL.

7. The surface enhanced Raman detection method based on laser induced deposition according to claim 1, wherein: In the step (1), the concentration of the particles to be measured is 0.001 - 0.5 mg / mL.

8. The surface-enhanced Raman detection method based on laser-induced deposition according to claim 1, characterized in that: In the step (2), the power density of the laser irradiation is 0.1~2.0 mW / μm 2 ; the spot diameter is 1~10 μm; and the irradiation time is 10~300 s.

9. The surface enhanced Raman detection method based on laser induced deposition according to claim 1, wherein: In the step (3), the methods for regulating the deposition morphology of gold nanoparticles and the particles to be measured include adjusting the laser power, spot radius, and solution physical properties of the mixed dispersion.

10. The surface enhanced Raman detection method based on laser induced deposition according to claim 1, characterized in that: In the step (5), the criteria for optimizing the enhancement effect of the surface-enhanced Raman scattering signal include maximizing the Raman signal intensity, improving the signal-to-noise ratio, and the consistency of spectral peak positions and full widths at half maximum.

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