Preparation method and SERS (Surface Enhanced Raman Scattering) application of nanogold polymer composite material

Abstract

The invention discloses a nanogold polymer composite material for surface enhanced Raman scattering (SERS) and a preparation method of the nanogold polymer composite material. The material is prepared from a monomer, a cross-linking agent, a photoinitiator, tetrachloroauric acid and water. The preparation method comprises the following steps: preparing a gold source precursor solution, preparing a photocuring premixed solution, mixing to form liquid photosensitive resin, carrying out ultraviolet light curing molding to form a composite film, and carrying out heat treatment to obtain a final product. According to the method, a reducing agent and subsequent purification are not needed, polymer generation and nanogold reduction are synchronously achieved through one-step photopolymerization, and the method is simple in process, mild in condition and environmentally friendly. The obtained nanogold is mainly triangular, polygonal and polyhedral, has rich tip and edge structures, is uniformly dispersed in a polymer without agglomeration, can effectively form SERS hot spots, and is suitable for an SERS substrate.

Description

Technical Field

[0001] This application relates to the field of surface-enhanced Raman scattering (SERS) substrate materials technology, and in particular to a nano-gold-polymer composite film prepared based on in-situ photopolymerization and thermal reduction and its application in SERS detection. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) is a highly sensitive, fast, and accurate spectroscopic analysis method that amplifies the Raman scattering signal of target molecules through nanoparticles or nanostructures on the substrate surface. It can also achieve non-destructive testing and has important application value in environmental analysis, biomedicine, and food safety.

[0003] Currently, the academic community generally believes that SERS (Surface Plasma Resonance Emission System) has two mechanisms: electromagnetic enhancement and chemical enhancement. The electromagnetic enhancement mechanism mainly originates from localized surface plasmon resonance generated by noble metal nanostructures or rough surfaces. Therefore, noble metal nanomaterials such as gold and silver are widely used in the preparation of SERS substrates. At the nanoscale, the tips and edges of noble metal nanostructures generate localized strong electric fields and tip effects, forming large electric field intensity regions, which are the "hot spots" required for SERS. Therefore, the SERS effect can be enhanced by controlling the morphology of noble metal particles and increasing the number of protrusions and tips.

[0004] Common methods for fabricating noble metal SERS substrates can be broadly categorized into "top-down" and "bottom-up" approaches. The "top-down" method primarily involves direct fabrication using photolithography and etching techniques, or a combination of these with template methods, such as the Klarite® SERS chip developed by Renishaw. This method can precisely fabricate highly ordered nanostructures, but it often requires specialized experimental equipment, resulting in high process complexity and cost, limited tunability, and the inability to synthesize anisotropic nanoparticles. The "bottom-up" method involves preparing metal nanoparticle sols through chemical synthesis, followed by self-assembly on a substrate or continued in-situ growth to obtain nanostructures. While this method offers less precision and stability in nanostructure control compared to the "top-down" approach, it requires no expensive specialized equipment and is more widely studied.

[0005] Composites of gold nanoparticles and polymers combine the physicochemical properties of noble metals with the ease of processing and molding of polymers, making them widely used in SERS substrates. The preparation methods for gold nanoparticle-polymer composites can be divided into two main categories: 1. Physical blending: Gold nanoparticles are synthesized beforehand and then blended with polymers. This method suffers from problems such as easy agglomeration and uneven dispersion of gold nanoparticles, and the preparation steps are cumbersome. Chemical synthesis of gold nanoparticles typically involves steps such as seed preparation, chemical reduction, seed growth, surface modification and protection, separation and purification, followed by mixing, dispersion, and drying with the polymer system. 2. In-situ synthesis: For example, reducing gold precursors (such as HAuCl4) in polymers allows gold nanoparticles to directly nucleate, grow, and uniformly disperse in situ within the polymer network. This method avoids the agglomeration problem of nanoparticles in physical blending methods, improving the uniformity and stability of the composite material.

[0006] The prior art discloses some related technologies, such as: "Polymer nanocomposites for plasmonics: In situ synthesis of gold nanoparticles after additive manufacturing" (Polymer Testing, 2023, 117:107869) discloses a polymer composite material in which gold nanoparticles are generated by in-situ reduction after photopolymerization and 3D printing followed by thermal treatment to dope the gold precursor KAuCl4 in a photoresist. However, it still has the following technical problems: First, the method uses KAuCl4 as the gold source, which introduces potassium ion impurities, easily causing background signal interference or non-specific interactions with the analyte molecules during surface-enhanced Raman scattering (SERS) detection, seriously affecting the detection sensitivity and reproducibility; second, because KAuCl4 has extremely low solubility in organic photoresist systems, only 0.1~1% has been achieved in the literature. The wt% doping amount results in insufficient gold nanoparticle content in the final composite material, making it difficult to form high-density plasma "hot spots" and significantly weakening the SERS enhancement factor. Furthermore, the post-processing needs to be carried out at a high temperature of 170℃, which can easily cause excessive relaxation of polymer chain segments, degradation of cross-linked networks, or even carbonization, resulting in a decrease in the mechanical strength of the film and morphological collapse, limiting its practical application in flexible or microstructured SERS substrates.

[0007] "In situ synthesis of gold-cross-linked poly(ethylene glycol) nanocomposites by photoinduced electron transfer and free radical polymerization processes" Chemical Communications, 2008 (24): 2771–2773. This paper discloses a method for directly dispersing HAuCl4 and the photoinitiator Irgacure 2959 in polyethylene glycol diacrylate (PEGDA), simultaneously achieving polymerization and gold ion reduction under ultraviolet light irradiation to generate gold nanoparticle / PEGDA composite films in situ. However, in practical applications, the following technical problems often exist: Since HAuCl4 is a strongly polar inorganic salt and PEGDA is a non-polar hydrophobic monomer, their interfacial compatibility is poor, leading to uneven dispersion of the gold precursor in the resin system. This easily results in localized supersaturation precipitation during photoreduction, forming gold nanoparticles with wide size distribution and severe aggregation, disrupting plasmon resonance consistency. Simultaneously, due to solubility limitations, the amount of HAuCl4 added is restricted to ≤5%. The wt% concentration makes it difficult to increase the density of SERS active sites. In addition, the system only uses the crosslinking monomer PEGDA and lacks low-viscosity diluent monomers (such as N,N'-dimethylacrylamide), resulting in poor leveling, uneven film thickness, and easy generation of microcracks during film formation, which seriously affects the spatial uniformity of SERS signal. More importantly, the reaction must be carried out in an inert nitrogen atmosphere to prevent free radical quenching, which is a harsh process condition and not conducive to large-scale preparation.

[0008] The paper "In situ synthesis of gold nanoparticles in polymer films underconcentrated sunlight: control of nanoparticle size and shape with solarflux" published in *Reaction Chemistry & Engineering*, 2019, 5(2): 330–341, discloses a technique for preparing gold / polymer composite films by spin-coating HAuCl4 with PMMA or potato starch in a solvent and then using simulated sunlight for in-situ reduction. However, it still has the following technical problems: when PMMA is used as the matrix, it is a linear non-crosslinked polymer with a low glass transition temperature (~105℃) and lacks nanoparticles that can interact with Au³⁺. + Or Au 0The functional groups (such as amide and carboxyl groups) in coordination cause gold nanoparticles to lack anchoring sites during nucleation and growth, tending to form isotropic spherical particles. This makes it impossible to effectively construct "hot spot" structures such as tips and gaps with high electromagnetic field enhancement effects. At the same time, PMMA has poor solvent resistance and is prone to swelling and deformation when in contact with common organic analytes (such as benzene compounds and alcohols), which damages the stability of the SERS substrate. While potato starch is biocompatible, its strong hydrophilicity causes it to soften or even dissolve upon contact with water after film formation, making it completely unsuitable for aqueous SERS detection scenarios and severely limiting its application scope.

[0009] 《In-situ photochemical synthesis of Au nanoparticles in polymermatrix with one-component thioxanthone disulfide for detection of benzene,toluene and xylene vapour》Progress in Organic Coatings, 2019, 132: 125–131. A method for in-situ synthesis of gold nanocomposite thin films for gas sensing based on a novel bifunctional photoinitiator TX-SS-TX, PEGDA and PEGMEA copolymer system via multiple UV irradiations (12–800 times) is disclosed. However, in practical applications, the following technical problems often exist: the preparation process requires repeated exposures to achieve sufficient reduction and polymerization, which is cumbersome, inefficient, and difficult to guarantee batch-to-batch consistency; more importantly, the obtained gold nanoparticles are mainly ellipsoidal or spherical, lacking sharp edges, nano-gap, and other efficient coupling structures for local surface plasmon resonance (LSPR), resulting in weak electromagnetic field enhancement effect and failing to meet the requirements of high-sensitivity SERS detection for "hot spot" density; in addition, this study did not optimize or verify the SERS performance, and its material design did not consider the nanostructure regulation required for Raman signal enhancement.

[0010] "In-situ synthesis and integration of gold nanoparticles into 3Dprinted optical fiber probes" Scientific Reports, 2024, 14(1): 29736. This paper discloses a method for first preparing HEMA / PEGDA photocurable optical fiber probes using 405 nm DLP 3D printing, and then immersing them in boiling Au³⁺. +A method for loading gold nanoparticles via post-reduction in solution is proposed; however, it still suffers from the following technical problems: In this two-step process, the generation of gold nanoparticles depends on high-temperature (~100℃) aqueous immersion, which not only has high energy consumption and low utilization rate of noble metal precursors (a large amount of unreacted HAuCl4 remains in the solution), but also the severe thermodynamic conditions easily lead to rapid and disordered reduction of gold ions, forming large-sized, polydisperse particles accompanied by severe agglomeration, which destroys the uniform distribution at the nanoscale; at the same time, although HEMA is hydrophilic, its crosslinking density is low and its mechanical modulus is small, which makes it prone to swelling or structural deformation under boiling conditions, affecting the geometric accuracy of the probe; most importantly, this method does not directly design the material as a SERS active substrate, nor does it optimize the gold content and distribution to match the requirements of SERS.

[0011] Patent CN104084597B (Applicant: Changchun Institute of Applied Chemistry, Chinese Academy of Sciences; Publication Date: 2014-10-08) discloses a method for preparing fractal aggregates of gold nanoparticles with surface-grafted polymers by mixing chloroauric acid with a solution of amino acrylate polymers, followed by stirring, sonication, and in-situ reduction. However, in practical applications, the following technical problems often exist: This method relies on organic solvents (such as THF and DMF) to dissolve the polymer, and subsequent solvent evaporation and removal require a long time. This not only results in a long process cycle and high energy consumption, but also the residual solvent may poison the SERS detection environment or interfere with the adsorption of the analyte molecules. In addition, the product is a discrete nanoparticle aggregate rather than a continuous thin film, which is difficult to directly integrate onto standard optical platforms (such as glass slides and microfluidic chips) for conventional SERS measurements. More importantly, this patent does not systematically evaluate the SERS performance of the material, nor does it solve key engineering problems such as the spatial arrangement, density control, and signal reproducibility of nanoparticles on the substrate.

[0012] The surface-enhanced Raman scattering (SERS) substrate-based gold-polymer composite material disclosed in this application can, to some extent, solve the technical problems existing in the prior art, such as low gold content, uneven distribution, lack of hot spots, complex processing, poor stability, and lack of targeted SERS design. Through careful design of the composition of the photosensitive prepolymer system, the generation of gold nanoparticles and polymers is achieved simultaneously in a one-step reaction. This achieves both good film-forming properties and control over the morphology and dispersion of the gold nanoparticles. The generated gold nanoparticles do not agglomerate and have morphologies mainly consisting of triangles, polygons, and polyhedra, with numerous sharp points and edge structures, which are conducive to generating the SERS effect. Summary of the Invention

[0013] To overcome the aforementioned problems in the prior art, the present invention provides a nano-gold polymer composite material that can be used as a surface-enhanced Raman scattering (SERS) substrate, comprising: monomer, crosslinking agent, photoinitiator; tetrachloroauric acid; and water.

[0014] Its preparation method includes the following steps in sequence: S1. Solution preparation: Dissolve the tetrachloroauric acid in water to form a gold source precursor solution; S2. Preparation of premix: The monomer, the crosslinking agent and the photoinitiator are mixed and stirred evenly to form a photocurable premix; S3. Photosensitive resin synthesis: The gold source precursor solution obtained in step S1 is mixed with the photocurable premix obtained in step S2, and the mixture is ultrasonically treated to make the components uniformly dispersed to obtain a liquid photosensitive resin containing the gold precursor. S4. Ultraviolet curing molding: The liquid photosensitive resin is coated into a film, placed in an air-isolated environment, and subjected to a cross-linking polymerization reaction under ultraviolet light irradiation to form a cured polymer composite film; S5. Heat treatment: The polymer composite film obtained in step S4 is subjected to heat treatment to finally obtain the nano-gold polymer composite film.

[0015] The monomer may be DMAAM or HEMA, or a mixture of the two.

[0016] The crosslinking agent may be one or more of PEGDA200, PEGDA400, PEGDA600, or PEGDA1000.

[0017] Preferably, the monomer is PEGDA200.

[0018] The ratio of monomer to crosslinking agent is between 1:3 and 3:1.

[0019] The initiator is photoinitiator 819DW or 2959, and the preferred addition amount is 3-9 parts.

[0020] The ultraviolet irradiation time is 2-12 minutes.

[0021] The mass ratio of HAuCl4 to water is 1:28 to 9:20.

[0022] Based on the above technical solution, this application achieves the following technical effects: In terms of materials and processes, this method avoids the use of external reducing agents and eliminates the need for subsequent separation and purification steps, thereby reducing the possibility of impurity introduction. The raw material system is simple, containing only tetrachloroauric acid, water, and photosensitive resin. The formation of gold nanoparticles and polymer generation are simultaneously achieved through a one-step reaction, resulting in a simple and efficient process. The reaction conditions are mild, producing no chemical waste or VOC emissions, thus conforming to green chemistry principles.

[0023] In terms of cost and economy, this method overcomes the shortcomings of some existing technologies, such as complex processes, violent reactions, long processing times, large amounts of precious metals, and low utilization rates. Through integrated reaction and purification-free design, it significantly reduces raw material consumption and processing costs, and improves material utilization efficiency.

[0024] In terms of the structure and performance regulation of gold nanoparticles, this method, through careful design of the composition of the photosensitive prepolymer system, not only achieves excellent film-forming properties but also effectively controls the morphology and dispersion of gold nanoparticles. The prepared gold nanoparticles are mainly triangular, polygonal, and polyhedral, with abundant pointed and edge structures, which are conducive to the formation of SERS hotspots. At the same time, the gold nanoparticles are uniformly dispersed in the polymer system without agglomeration and have good stability, providing a reliable guarantee for SERS applications. Attached Figure Description

[0025] Figure 1 Surface morphology of the nano-gold polymer composite film obtained in Example 1.

[0026] Figure 2 Surface morphology of the nano-gold polymer composite film obtained in Example 2.

[0027] Figure 3 Surface morphology of the nano-gold polymer composite film obtained in Example 3.

[0028] Figure 4 Example 1 uses the Raman spectra of R6G molecules on different surfaces.

[0029] Figure 5 Example 1 uses Raman spectra of CV molecules on different surfaces.

[0030] Figure 6 Example 2: Raman spectra of R6G molecules on different surfaces.

[0031] Figure 7 Example 3 uses the Raman spectra of R6G molecules on different surfaces.

[0032] Figure 8 SEM image of Comparative Example 1.

[0033] Figure 9 SEM images of Comparative Example 2.

[0034] Figure 10 SEM images of Comparative Example 3.

[0035] Figure 11 SEM images of Comparative Example 4.

[0036] Figure 12 SEM images of Comparative Example 5.

[0037] Figure 13 SEM images of Comparative Example 6.

[0038] Figure 14 Patterned nano-gold polymer composite materials. Detailed Implementation

[0039] Example 1 raw material: (1) Monomer: 75 parts of N,N'-dimethylacrylamide (DMAAM); (2) Crosslinking agent: 25 parts of polyethylene glycol diacrylate (PEGDA200) with a molecular weight of 200, i.e., the ratio of monomer to crosslinking agent is 3:1; (3) 5 parts of photoinitiator 819DW, that is, the amount of photoinitiator is 5% of the total amount of monomer and crosslinking agent; (4) 9 parts of tetrachloroauric acid (HAuCl4), that is, the ratio of tetrachloroauric acid to polymer matrix (total parts of monomer and crosslinking agent) is 9:100; (5) 20 parts water, that is, the total amount of tetrachloroauric acid and water is 29 parts; The preparation method includes the following steps: (1) Dissolve HAuCl4 in water to prepare a solution; (2) Mix the monomer, crosslinking agent, and photoinitiator and stir until homogeneous; (3) Mix the two liquids obtained in the first two steps, and then mix them evenly by ultrasonication to obtain liquid photosensitive resin; (4) The liquid photosensitive resin is coated onto the surface of a glass slide, and another glass slide is placed on top to isolate it from the air. Then, the photosensitive resin is applied at a wavelength of 365 nm and a power density of 45 mW / cm². 2 Irradiated with a UV-LED ultraviolet light source for 10 minutes, then the glass slide was removed to obtain a solid film; (5) Place the film obtained in the previous step on a hot plate at 120°C and heat for 120 minutes.

[0040] Example 2 Raw materials: (1) Monomer: 75 parts of hydroxyethyl methacrylate (HEMA); (2) Crosslinking agent: PEGDA200 25 parts, that is, the ratio of monomer to crosslinking agent is 3:1; (3) Photoinitiator: 5 parts of 819DW, that is, the amount of photoinitiator is 5% of the total amount of monomer and crosslinking agent; (4) HAuCl41 parts, that is, the ratio of tetrachloroauric acid to polymer matrix (total parts of monomer and crosslinking agent) is 1:100; (5) Solvent: 28 parts water, that is, the total amount of water and tetrachloroauric acid is 29 parts; The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0041] Example 3 (1) Monomer: 75 parts of DMAAM; (2) Crosslinking agent: PEGDA200 25 parts, that is, the ratio of monomer to crosslinking agent is 3:1; (3) Photoinitiator: 5 parts of 819DW, that is, the amount of photoinitiator is 5% of the total amount of monomer and crosslinking agent; (4) 1 part of HAuCl; (5) Solvent: 28 parts water, that is, the total amount of water and tetrachloroauric acid is 29 parts; The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0042] Characterization and performance testing of SERS substrate Scanning electron microscopy (SEM) characterization: The morphology of gold particles on the thin film surface was observed using SEM. For Example 1 (see...) Figure 1 Example 2 (see Example 2) Figure 2 ) and Example 3 (see Example 3) Figure 3 In both cases, it can be observed that the gold nanoparticles are uniformly distributed in the polymer matrix without agglomeration, proving that the preparation method described in this invention can obtain composite films with good uniformity and film-forming properties. Most of the gold nanoparticles are triangular, hexagonal, or polyhedral in shape, with a large number of sharp and edge structures, which is conducive to the formation of abundant SERS hotspots.

[0043] Both Examples 1 and 3 used DMAAM monomers, and the resulting films contained gold nanoparticles that were predominantly polyhedral with abundant sharp and edge structures. In Example 1, due to the higher concentration of HAuCl4 in the reaction system, the resulting film contained gold particles with larger average size, more diverse morphologies, and a higher gold particle distribution density. This demonstrates that the preparation method described in this invention can alter the morphology and distribution density of gold particles in the film, thereby controlling the distribution of SERS hotspots.

[0044] SERS performance evaluation The gold nanoparticle polymer composite films obtained in Examples 1-3 were used as SERS substrates, and Rhodamine 6G (R6G) and crystal violet (CV) dyes were used as probe molecules to prepare solutions with concentrations of 1×10⁻⁶. -3 mol / L, 1×10 -4 mol / L, 1×10 - 5 mol / L, 1×10 -6A mol / L aqueous solution was prepared. The SERS substrate was immersed in the probe molecule solution for 2 hours, then removed, rinsed with distilled water, and air-dried. The Raman spectra of the dye molecules on the SERS substrate were then detected by a micro-area laser Raman spectrometer.

[0045] A single-crystal silicon wafer was used as the control sample for SERS, with a concentration of 1×10⁻⁶. -3 A mol / L aqueous solution of probe molecules was dropped onto the surface of a silicon wafer and allowed to dry naturally. The Raman spectra of the dye molecules on the silicon wafer were then collected using a Raman spectrometer.

[0046] The analytical enhancement factor is calculated using formula (1). AEF Evaluate the enhancement effect of the SERS substrate on the Raman scattering intensity of probe molecules: (1) in: I SERS This indicates the peak intensity of the Raman spectrum obtained by measuring the dye molecules on a SERS substrate; I Raman This indicates the peak intensity of the Raman spectrum obtained by measuring the dye molecules on the silicon wafer; C SERS This indicates the concentration of dye molecules immersed in the SERS substrate, in mol / L. This indicates the concentration of dye molecules dropped onto the silicon wafer, expressed in mol / L.

[0047] For Example 1, when R6G was used as the probe molecule, the obtained spectrum is as follows: Figure 4 As shown. Spectral line a is 1×10 -3 Raman spectrum of R6G at mol / L on silicon wafer surface.

[0048] The spectral lines b to e are 1×10⁻⁶ respectively. -6 mol / L, 1×10 -5 mol / L, 1×10 -4 mol / L and 1×10 -3 Raman spectra of mol / L R6G on the SERS substrate obtained in Example 1.

[0049] All spectral lines were acquired using the following conditions: excitation wavelength of 785 nm, laser power of 5 mW, integration time of 30 s, objective magnification of 100, and objective numerical aperture of 0.8.

[0050] For Example 1, when CV was used as the probe molecule, the obtained spectrum is as follows: Figure 5 As shown. All spectral lines were acquired using the following conditions: excitation wavelength 785 nm, laser energy 5 mW, integration time 30 s, objective magnification 100, and objective numerical aperture 0.8. Spectral line a is 1 × 10⁻⁶. -3 Raman spectra of CV at mol / L on silicon wafer surface.

[0051] The spectral lines b to d are 1×10⁻⁶ respectively. -5 mol / L, 1×10 -4 mol / L and 1×10 -3 Raman spectra of mol / L CV on the SERS substrate obtained in Example 1.

[0052] from Figure 4 and Figure 5 It can be seen that the concentration is 1×10 -3 The Raman scattering signal of the probe molecule R6G and CV on the silicon wafer surface is extremely weak when mol / L; however, when the same or even lower concentrations of dye are applied to the SERS substrate described in Example 1, the characteristic spectral line of the R6G molecule (1186 cm⁻¹) can be detected. -1 1315 cm -1 1366 cm -1 1514 cm -1 and 1655 cm -1 ) and the characteristic spectral lines of CV molecules (1178 cm⁻¹) -1 1382 cm -1 1588 cm -1 1624 cm -1 The spectral intensity increased significantly, demonstrating that the nano-gold polymer composite film prepared in Example 1 exhibits the SERS effect, with a detection limit of 10 for R6G and CV molecules. -4 The concentration is on the order of mol / L. According to formula (1), the AEF values ​​for R6G and CV molecules can reach 78.6 and 1.7 × 10⁻⁶, respectively. 3 .

[0053] For Example 2, when R6G was used as the probe molecule, the obtained spectrum is as follows: Figure 6 As shown. All spectral lines were acquired using the following conditions: wavelength 785 nm, laser energy 1.129 mW, integration time 30 s, objective magnification 40, and objective numerical aperture 0.75. Spectral line a has a value of 1 × 10⁻⁶. -3 Raman spectrum of mol / L R6G on silicon wafer surface.

[0054] The spectral lines b to e are 1×10-6 mol / L, 1×10 -5 mol / L, 1×10 -4 mol / L and 1×10 -3 Raman spectra of mol / L R6G on the SERS substrate obtained in Example 2.

[0055] For Example 2, as Figure 6 As shown in spectral line a, the concentration is 1×10 -3 The Raman scattering signal of the probe molecule R6G and CV on the silicon wafer surface is extremely weak when using the SERS substrate described in Example 2, with a concentration of 1×10⁻⁶. -4 ~ 1×10 -3 The Raman scattering signal of R6G at mol / L was significantly enhanced, but as the R6G concentration continued to decrease, it became difficult to observe a significant Raman scattering peak. The detection limit of the SERS substrate obtained in Example 2 also reached 10 mol / L. -4 The mol / L level is calculated according to formula (1). AEF It is 26.8.

[0056] For Example 3, when R6G was used as the probe molecule, the obtained spectrum is as follows: Figure 7 As shown. All spectral lines were acquired using the following conditions: wavelength 532 nm, laser energy 0.22 mW, integration time 30 s, objective magnification 40, and objective numerical aperture 0.75.

[0057] Where spectral line a is 1×10 -3 The Raman spectral lines b~d of mol / L R6G on the silicon wafer surface are 1×10⁻⁶. - 5 mol / L, 1×10 -4 mol / L and 1×10 -3 Raman spectra of mol / L R6G on the SERS substrate obtained in Example 3.

[0058] Compared to Example 1, the amount of HAuCl4 in Examples 2 and 3 was significantly reduced, directly affecting the distribution density of gold nanoparticles in the substrate. When the amount of HAuCl4 was reduced to 1 / 9 of that in Example 1, that is, when the amount of the noble metal compound HAuCl4 was only 1% of the polymer matrix, the SERS effect could still be generated. This proves the feasibility of the material preparation method described in this invention when applied to SERS substrates.

[0059] Comparative Examples The following are some comparative embodiments used to demonstrate the technical effects of the technical solution of the present invention.

[0060] Comparative Example 1 raw material: (1) 100 parts of PEGDA200; (2) 5 parts of photoinitiator 819DW, that is, the amount of photoinitiator is 5% of the total amount of monomer and crosslinking agent; (3) 9 parts of tetrachloroauric acid (HAuCl4), that is, the ratio of tetrachloroauric acid to polymer matrix (total parts of monomer and crosslinking agent) is 9:100; (4) 20 parts water, that is, the total amount of tetrachloroauric acid and water is 29 parts; That is, compared to Example 1, DMAAM monomers are not used.

[0061] The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0062] Comparative Example 2 raw material: (1) 75 parts of ethoxylated trimethylolpropane triacrylate (EO-TMPTA) and 25 parts of PEGDA200; (2) 5 parts of photoinitiator 819DW, i.e., the amount of photoinitiator is 5% of the total amount of monomer and crosslinking agent; (3) 9 parts of HAuCl4, that is, the ratio of tetrachloroauric acid to polymer matrix (total parts of monomer and crosslinking agent) is 9:100; (4) 20 parts water, that is, the total amount of tetrachloroauric acid and water is 29 parts; That is, compared to Example 1, the monomer is changed to EO-TMPTA; The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0063] Comparative Example 3 raw material: The reactants are the same as in Example 1.

[0064] Preparation steps: (1) Dissolve HAuCl4 in water to prepare a solution; (2) Mix the monomer, crosslinking agent and photoinitiator and stir evenly. Then coat it on the surface of a glass slide and cover it with another glass slide to isolate it from the air. Then irradiate it for 10 minutes under a UV-LED ultraviolet light source with a wavelength of 365 nm and a power density of 45 mW / cm2. Then remove the glass slide to obtain a polymer film. (3) The obtained polymer film was immersed in HAuCl4 aqueous solution until absorption saturation, then removed and irradiated under UV-LED ultraviolet light source for 10 minutes. (4) Place the film obtained in the previous step on a hot plate at 120°C and heat for 120 minutes.

[0065] Compared to Example 1, the preparation of the polymer film and the reduction of HAuCl4 were carried out separately.

[0066] Comparative Example 4 raw material: (1) Monomer: 75 parts of DMAAM; (2) Crosslinking agent: PEGDA200 25 parts; (3) Photoinitiator: 5 parts ITX, i.e., change the type of photoinitiator used; (4) 9 parts of HAuCl4, that is, the ratio of tetrachloroauric acid to polymer matrix (total parts of monomer and crosslinking agent) is 9:100; (5) 20 parts water, that is, the total amount of tetrachloroauric acid and water is 29 parts; That is, compared to Example 1, the photoinitiator used is a thioxanthone compound ITX.

[0067] The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0068] Comparative Example 5 raw material: (1) Monomer: 75 parts of DMAAM; (2) Crosslinking agent: PEGDA200 25 parts; (3) Photoinitiator: 1173 5 parts; (4) 9 parts of HAuCl4; (5) 20 parts water, that is, the total amount of tetrachloroauric acid and water is 29 parts; That is, compared to Example 1, the photoinitiator used is model 1173.

[0069] The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0070] Comparative Example 6 raw material: (1) Monomer: 75 parts of DMAAM; (2) Crosslinking agent: PEGDA200 25 parts; (3) Photoinitiator: 5 parts of 819DW; (4) 0.5 parts of HAuCl4, that is, the ratio of tetrachloroauric acid to polymer matrix (total parts of monomer and crosslinking agent) is 0.5:100; (5) Solvent: 29 parts water, that is, the total amount of water and tetrachloroauric acid is 29.5 parts; That is, compared with Examples 1-3, the amount of HAuCl4 added is significantly reduced.

[0071] The preparation method of the nano-gold polymer composite film is the same as that in Example 1.

[0072] SEM images of the samples obtained from the above comparative examples are shown below. Figure 8-13 As shown, the sample has the following problems: In summary, the samples in Comparative Examples 1-6 exhibited issues such as gold particle aggregation or uneven distribution, excessively small and sparsely distributed gold particles, and poor film formation quality and surface condition, all of which prevented the generation of a reliable and stable SERS effect.

[0073] SERS application The material proposed in this invention can be combined with mask exposure, printing technology, coating technology, stereolithography technology, etc., to create patterns in two-dimensional planes or three-dimensional space, enabling further applications.

[0074] Using the material formulation and preparation process described in Example 1, a patterned negative mask was used. After exposure, deionized water was used for development to remove the unexposed areas, resulting in a patterned nano-gold polymer composite material on a glass substrate. Figure 14 As shown.

[0075] While the specific embodiments of this disclosure have been described above, they are not intended to limit the scope of protection of this disclosure. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this disclosure are still within the scope of protection of this disclosure.

Claims

1. A nano-gold polymer composite material, characterized in that, It is made from monomers, crosslinking agents, photoinitiators, tetrachloroauric acid, and water, and its preparation method is as follows: The nano-gold polymer composite material is formed by mixing an aqueous solution containing tetrachloroauric acid with a photocurable premix containing monomers, crosslinking agents and photoinitiators, followed by ultrasonic dispersion, UV curing, crosslinking to form a film, and heat treatment.

2. A nano-gold polymer composite material according to claim 1, characterized in that: The monomer is DMAAM, HEMA, or a combination thereof.

3. A nano-gold polymer composite material according to claim 1, characterized in that: The crosslinking agent is PEGDA with a molecular weight of 200 to 1000.

4. A nano-gold polymer composite material according to claim 1, characterized in that: The monomer is PEGDA with a molecular weight of 200.

5. A nano-gold polymer composite material according to claim 1, characterized in that: The ratio of monomer to crosslinking agent is 1:3 to 3:

1.

6. A nano-gold polymer composite material according to claim 1, characterized in that: The photoinitiator is 819DW or 2959.

7. A nano-gold polymer composite material according to claim 1, characterized in that: The ultraviolet irradiation time is 2 to 12 minutes.

8. A nano-gold polymer composite material according to claim 1, characterized in that: The mass ratio of tetrachloroauric acid to water is 1:28 to 9:

20.

9. An application of the nano-gold polymer composite material according to claim 1, characterized in that: It can be used in combination with mask exposure, printing technology, coating technology, or stereolithography technology to create patterns in two-dimensional planes or three-dimensional space.

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