A slsp-sers dual spectrum combined detection method

Abstract

The present application belongs to the technical field of spectral detection, and particularly relates to a SLSP-SERS dual-spectrum combined detection method. The method comprises the following steps: step 1, obtaining a silver nanowire (AgNW) network film; step 2, obtaining SLSP sensing microstructure parameters; step 3, obtaining a SLSP sensing microstructure composed of the silver nanowire network film according to the structure parameters; step 4, adding a to-be-detected substance on the SLSP sensing microstructure composed of the silver nanowire network film, and performing SERS spectral detection and SLSP enhanced back-transmission spectrum detection; and step 5, combining the SERS spectral detection and the SLSP enhanced back-transmission spectrum detection to obtain the frequency spectrum obtained respectively, and analyzing the to-be-detected substance. The method retains the high sensitivity and molecular structure recognition ability of SERS, and also solves the problem that the single SERS detection technology cannot realize accurate quantitative detection.

Description

Technical Field

[0001] This invention belongs to the field of spectral detection technology, specifically relating to a dual-spectrum detection method using SLSP-SERS. Background Technology

[0002] Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive spectroscopic detection technique capable of detecting molecules at the single-molecule level. Its Raman spectral information can also serve as an optical fingerprint for effective identification of molecular structures, offering significant advantages in detecting trace targets in mixed solid-liquid-gas mixtures. However, the ultrasensitive nature of SERS spectroscopy primarily stems from the strong electromagnetic field enhancement caused by localized surface plasmon resonances. Surface plasmon resonances are collective oscillations of numerous free electrons within a material (typically metals). The enhanced electromagnetic field is closely related to the micro- and nano-scale morphology of the metal surface and decays exponentially with distance along the surface normal, exhibiting a strong dependence on micro-surface morphology. This localized enhancement characteristic means that the SERS signal intensity is greatly affected by the adsorption position of the detected molecule on the metal surface, leading to poor repeatability and insufficient stability, making accurate quantitative detection difficult with a single SERS detection technique.

[0003] In recent years, a novel detection technique based on Spoof Localized Surface Plasmons (SLSP) has been reported in the field of biochemical sensing. The principle of SLSP is based on the surface-bound modes of microwave or terahertz (GHz-THz) electromagnetic waves existing in subwavelength metallic microstructures. The resonant characteristics of these surface-bound modes mainly depend on the dielectric environment and geometric parameters of the microstructure, and can be used to sense the dielectric constant of materials near the microstructure. Since SLSP characteristics represent a holistic response to the entire medium near the microstructure, this gas detection technique avoids the quantitative detection limitations caused by the micro-surface morphology dependence in SERS detection. However, it cannot achieve precise identification of trace molecular structures and concentration distributions in complex atmospheres. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a SERS-SLSP dual-spectrum detection method based on a silver nanowire (AgNW) network microstructure. This method retains the high sensitivity and molecular structure recognition capability of SERS, while also solving the problem that single SERS detection techniques are insufficient for accurate quantitative detection.

[0005] The SLSP-SERS dual-spectrum detection method of this invention includes:

[0006] Step 1: Obtain a silver nanowire (AgNW) network film;

[0007] Step 2: Obtain the microstructure parameters of the SLSP sensor;

[0008] Step 3: According to the structural parameters, obtain the SLSP sensing microstructure composed of a silver nanowire network film;

[0009] Step 4: The substance to be detected is dropped onto the SLSP sensing microstructure composed of silver nanowire network film, and SERS spectroscopy and SLSP enhanced back-transmission spectroscopy are performed.

[0010] Step 5: Analyze the detected substance by combining the spectra obtained from SERS spectroscopy and SLSP enhanced back-transmission spectroscopy.

[0011] Furthermore, the silver nanowires in the silver nanowire network film are prepared by chemical synthesis.

[0012] Furthermore, the silver nanowire network film is prepared by spraying onto a substrate material.

[0013] Furthermore, the substrate material is one of filter paper, glass, or plastic.

[0014] Furthermore, in step 2, the SLSP sensing microstructure parameters enable the SLSP sensing microstructure composed of silver nanowire network film to have a high quality factor and multiple polarities.

[0015] Furthermore, the structural parameters are obtained by optimizing the structural parameters of the SLSP microstructure using the finite element method;

[0016] Furthermore, in step 2, the optimization of the SLSP sensing microstructure parameters is a collaborative optimization that simultaneously enhances the SERS signal target.

[0017] Furthermore, the collaborative optimization also optimizes the micro-nano structure parameters of the silver nanowire network film, with the optimization targets being high conductivity and high transmittance.

[0018] Furthermore, the micro / nano structure parameters include the aspect ratio and arrangement density of the silver nanowires.

[0019] Furthermore, in step 3, SLSP sensing microstructures are fabricated on the silver nanowire network film using laser engraving or photolithography.

[0020] The principle and beneficial effects of this invention are as follows:

[0021] SERS spectroscopy and SLSP-enhanced transmission / reflection spectroscopy, two gas detection techniques based on electromagnetic spectrum (visible light, terahertz-microwave), each have their advantages and disadvantages and can complement each other. Their combined use has enormous application potential. Silver nanowires (Ag Nanowires, AgNWs), as a classic surface plasmon micro / nanostructure, possess electromagnetic field enhancement capabilities in the visible light band and are widely used in SERS detection. Furthermore, AgNW network films with high aspect ratios and high conductivity also possess many advantages such as good light transmittance, uniform conductivity, and good flexibility. Since highly conductive AgNW network films exhibit near-perfect conductor properties in the low electromagnetic frequency band, it becomes possible to fabricate high-transmittance SLSP microstructures based on AgNWs. Further experiments confirmed that the microstructures fabricated from AgNW networks exhibit SLSP characteristics in the microwave band, and their resonant-enhanced reflection spectrum shows a sensitive response to the surrounding medium. Therefore, the AgNW network microstructure can achieve both plasmon enhancement of the SERS spectrum and sensitive response of the SLSP enhanced transmission / reflection spectrum, making it an ideal carrier for SERS-SLSP dual-spectrum detection technology.

[0022] This invention effectively combines the advantages of SERS spectroscopy and SLSP sensing while overcoming the shortcomings of each technology in detection. It has enormous application potential in the field of high-sensitivity and high-accuracy detection of trace substances in complex environments. It demonstrates significant application value in the high-sensitivity and high-accuracy detection of solids, liquids, and gases. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the process of dual-spectrum detection based on the AgNW network microstructure in an embodiment of the present invention.

[0024] Figure 2 This is an electron microscope image of the AgNW network film in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the planar structure of an exemplary SLSP microstructure in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of an exemplary SLSP reflection spectrum with multiple polar states in an embodiment of the present invention;

[0027] Figure 5 The electric field distribution diagrams of resonance peaks of different resonance modes in the SLSP microstructure are exemplary embodiments of the present invention.

[0028] Figure 6 The images shown are exemplary photographs and partial electron microscope images of AgNW network microstructures prepared by laser engraving in this embodiment of the invention.

[0029] Figure 7This is a schematic diagram illustrating the results of SERS detection of PATP molecules on an exemplary AgNW network microstructure in an embodiment of the present invention. Detailed Implementation

[0030] The technical method of the present invention will be described below through specific embodiments. The SLSP-SERS coupled detection process in this embodiment is basically as follows: Figure 1 As shown, it specifically includes the following structures:

[0031] The first step is the preparation of the AgNW network membrane;

[0032] AgNW was prepared using chemical synthesis methods and then coated onto various substrates such as filter paper, glass, and plastics using a spraying method. Figure 2 The AgNW network membrane shown;

[0033] The second step is microstructure parameter optimization.

[0034] The structural parameters of the SLSP microstructure were optimized using methods such as the finite element method to obtain high quality factor and multipolar state SLSP sensing microstructure parameters.

[0035] For example, simulating such a problem using the finite element method Figure 3 The structural parameters of the classic SLSP microstructure shown in the figure are optimized. The structure is a disk with radial symmetry. The radius of the disk is r2 and the diameter is D. On the disk, the area from the center of the disk to the radius r1 is a complete circular surface. The part from the radius r1 to the outer contour of the disk is evenly divided into multiple fan-shaped structures by multiple slits evenly distributed around the center of the disk. The width of the widest part (the outer contour of the disk) is a, and the length of the fan-shaped structure is l. Obviously, l = r2 - r1. One of the strip structures extends a rectangular handle structure to the outer edge of the disk. The width of the handle structure is w. It is easy to see that w = a in the figure. The width of the handle structure is L. Therefore, for this classic SLSP microstructure, the optimizable geometric structural parameters include, but are not limited to, r2, r1, D, l, a, w, and L.

[0036] In spectroscopy, the quality factor is the ratio of the peak width to the peak position (frequency) of a resonance peak; it can be intuitively understood as the width of the resonance peak. A higher quality factor results in a narrower resonance peak. In spectral sensing, changes in external physical quantities (such as refractive index) cause changes in the peak position of the spectral peak. Shifting the same frequency, a narrower peak is easier to identify, thus increasing the sensing sensitivity.

[0037] Multipolarity refers to a spectrum containing multiple resonance peaks. Figure 5The example given is an SLSP reflection spectrum with multiple resonance peaks; each resonance peak has a different resonance mode, which can be identified by the electric field distribution at the frequency of that resonance peak, such as monopole, dipole, quadrupole, etc. Figure 4 The diagram illustrates the electric field distribution formed on the microstructure by the resonance peak frequencies of different resonance modes.

[0038] Multipolarity means that multiple resonance peaks can be used for sensing. High polarity generally has a higher quality factor. Multipolarity allows multiple resonance peaks to be located in a wider frequency range, such as the GHz-THz range, which is more conducive to detection. Under the premise of clearly defined optimization objectives, the specific optimization process based on simulation is well known to those skilled in the art and will not be elaborated here.

[0039] The third step is the fabrication of AgNW network microstructures;

[0040] Based on optimized structural parameters, various methods such as laser engraving and photolithography are used to etch or deposit microstructures into AgNW network films, resulting in... Figure 6 The microstructure shown is composed of AgNW network membranes.

[0041] The fourth step is SERS spectral detection;

[0042] The analyte was dropped onto the AgNW network microstructure and then subjected to SERS spectroscopy.

[0043] Figure 7 The paper presents an exemplary SERS spectrum obtained after adding PATP molecules to an exemplary Ag nanowire network structure, showing the spectral characteristic peaks corresponding to PATP molecules, demonstrating the effectiveness of Ag nanowire network structure for molecular SERS detection.

[0044] Step 5, SLSP sensor detection;

[0045] The analyte added to the AgNW network microstructure was then subjected to SLSP enhanced reverse transmission spectroscopy detection.

[0046] When the microstructure prepared by the AgNW network is in an air environment (BARE), the resonance peak of its SLSP spectrum is located at 210.9 kHz. However, after adding oil, the reflection peak of the oil in the microstructure's SLSP spectrum is located at 218.29 kHz, indicating a frequency shift in the SLSP resonance peak. This demonstrates that the resonance peak position of the SLSP spectrum of the microstructure prepared by the AgNW network changes with the refractive index of the environment. This allows for effective quantitative detection of SLSP spectra.

[0047] Step 6: SLSP-SERS dual-spectral analysis;

[0048] The analysis of detected substances is achieved by combining SLSP and SERS dual-spectral analysis. SLSP responds to the refractive index of the entire region near the microstructure. In single-substance detection, the frequency shift of the SLSP resonance peak corresponds one-to-one with the substance concentration (amount). However, this approach has limitations for detecting mixtures of multiple substances. SERS, as an optical fingerprint, can identify the molecular structure of substances through its spectral characteristic peaks, which is beneficial for identifying individual substances in mixtures. However, SERS mainly detects the visible light-enhanced region (subwavelength region, not the whole) in the microstructure, resulting in insufficient overall quantification. The combined SLSP and SERS dual-spectral analysis complements each other, offering significant advantages for the quantitative detection of trace mixtures.

[0049] In addition, it is worth noting that Ag nanowire network microstructures can enhance not only SERS signals but also SLSP signals by optimizing geometric and micro / nano structural parameters (such as the density of Ag nanowire networks and the aspect ratio of Ag nanowires). These two enhancements have different requirements for structural parameters, but they can be coordinated through optimization to achieve synergistic enhancement. In addition to synergistic effects with the aforementioned objectives, the optimization goals of micro / nano structures can also consider high conductivity and high light transmittance.

[0050] As can be seen from the above, the SLSP-SERS coupled detection method in this embodiment utilizes the microstructure prepared by the AgNW network to retain the high sensitivity and molecular structure recognition ability of SERS while simultaneously introducing SLSP detection and quantitative analysis. Molecular structure recognition and quantification can be achieved by adding the analyte in a single drop. It has many advantages such as mature process, convenient measurement, high stability and long service life.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-spectrum detection method using SLSP-SERS, characterized in that, include: Step 1: Obtain a silver nanowire network film; Step 2: Obtain the microstructure parameters of the SLSP sensor; Step 3: According to the structural parameters, obtain the SLSP sensing microstructure composed of a silver nanowire network film; Step 4: The substance to be detected is dropped onto the SLSP sensing microstructure composed of silver nanowire network film, and SERS spectroscopy and SLSP enhanced back-transmission spectroscopy are performed. Step 5: Analyze the detected substance by combining the spectra obtained from SERS spectral detection and SLSP enhanced back-transmission spectral detection respectively.

2. The method according to claim 1, characterized in that, The silver nanowires in the silver nanowire network film are prepared by chemical synthesis.

3. The method according to claim 1, characterized in that, The silver nanowire network film is prepared by spraying onto a substrate material.

4. The method according to claim 3, characterized in that, The substrate material is one of filter paper, glass, or plastic.

5. The method according to claim 1, characterized in that, In step 2, the parameters of the SLSP sensing microstructure enable the SLSP sensing microstructure composed of silver nanowire network film to have a high quality factor and multiple polarities.

6. The method according to claim 5, characterized in that, The structural parameters were obtained by optimizing the structural parameters of the SLSP microstructure using the finite element method.

7. The method according to claim 6, characterized in that, In step 2, the optimization of the SLSP sensing microstructure parameters is a collaborative optimization that simultaneously enhances the SERS signal target.

8. The method according to claim 7, characterized in that, The collaborative optimization also optimizes the micro-nano structure parameters of the silver nanowire network film, with the optimization goals being high conductivity and high transmittance.

9. The method according to claim 8, characterized in that, The micro / nano structure parameters include the aspect ratio and arrangement density of the silver nanowires.

10. The method according to claim 8, characterized in that, In step 3, SLSP sensing microstructures are fabricated on the silver nanowire network film using laser engraving or photolithography.

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