A wide-band, multi-composite mechanism surface-enhanced Raman scattering substrate

Abstract

The present invention relates to a wide-band, multi-composite mechanism-based surface enhanced Raman scattering substrate, comprising a substrate and a nanocomposite structure randomly distributed on the substrate, wherein the nanocomposite structure is etched on the substrate by a photolithography process or deposited on the substrate by a chemical synthesis method; the nanocomposite structure comprises a rod-shaped nanostructure and two sheet-shaped nanostructures, wherein the rod-shaped nanostructure is sandwiched between the two sheet-shaped nanostructures and connected to the two sheet-shaped nanostructures. The present invention solves the shortcomings of the existing surface enhanced Raman scattering substrates, such as low sensitivity and narrow band range of resonance peaks of enhanced Raman signals. Under the action of the composite mechanism principle, the local electric field on the surface of the nanocomposite structure is greatly enhanced. At the same time, the resonance peak range of the nanocomposite structure can be adjusted by changing the size and position of the rod-shaped nanostructure, which is wider than the band range of a single nanostructure.

Description

Technical Field

[0001] The invention relates to the field of pollutant and food safety detection, and in particular to a surface enhanced Raman scattering substrate with a wide band and a multi-composite mechanism principle. Background Art

[0002] As a powerful spectral detection technology, Raman spectroscopy has important applications in pollutant detection, food safety, biomolecule detection and other fields due to its advantages such as non-contact, non-destructive, high sensitivity and fast response speed. In Raman spectroscopy detection, the structure of the substrate is a very important part. The spectral signal obtained by ordinary Raman substrates is relatively weak, which limits the application of Raman spectroscopy detection technology in real life. However, by specially constructing the substrate, especially assembling a metal nanoparticle film on the surface of the substrate, under the action of the incident excitation light source, a strong local electric field will be formed on the surface of the metal nanoparticles, which can strongly amplify the generated Raman signal, so that the analysis of extremely low detection molecules can be achieved, thus becoming a trace detection method with great practical value.

[0003] The material, morphology, size of metal nanoparticles and the dielectric environment around them all have an important influence on the local electric field resonance peak on the surface of metal nanoparticles. Theoretical and experimental research results show that metal nanoparticles with pointed structures will form a "hotspot" at the tip due to the large radius of curvature of the tip under the action of the lightning rod effect. The local electric field generated at the "hotspot" is stronger. Therefore, a better Raman enhancement effect can be obtained by utilizing the "hotspot" characteristics of the pointed metal nanoparticles.

[0004] However, when applied to the field of pollutant and food safety detection, due to the very low relative content of the substance to be detected, the surface-enhanced Raman scattering substrate composed of metal nanoparticles with a sharp morphology is often still unable to detect the standard limit of pollutants and food harmful substances, not to mention the conventional metal nanoparticle surface-enhanced Raman scattering substrate, such as the silver nanocluster surface-enhanced Raman scattering substrate and its preparation method and application in patent CN109187487A. The invention uses electrochemical replacement reaction to prepare silver nanoclusters on silicon wafers, and uses surfactants to regulate the size and nanogaps of silver nanoclusters to obtain a surface-enhanced Raman scattering substrate with "hot spots". When the surface-enhanced Raman scattering substrate prepared by the above method detects rhodamine 6G molecules, the detection limit is 10 -16 mol / L, and for pollutants and food harmful substances with lower concentrations, it still cannot meet the needs of practical applications. Therefore, the preparation of surface-enhanced Raman scattering substrates with higher sensitivity and simpler process is still a difficult problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a surface enhanced Raman scattering substrate with a wide band and a multi-composite mechanism principle to solve the shortcomings of the existing surface enhanced Raman scattering substrate with low sensitivity and a narrow range of the resonance peak of the enhanced Raman signal. The surface enhanced Raman scattering substrate includes a substrate and a nanocomposite structure. The nanocomposite structure is composed of a noble metal rod-shaped nanostructure and two sheet-shaped nanostructures. The rod-shaped nanostructure and the two sheet-shaped nanostructures have a composite resonance enhancement characteristic. Compared with the local electric field on the surface of a single rod-shaped nanostructure or a sheet-shaped nanostructure, under the action of the composite mechanism principle, when the resonance peaks of the two are matched, the local electric field on the surface of the combined nanocomposite structure is greatly enhanced. At the same time, the resonance peak range of the nanocomposite structure can be regulated by changing the size of the sheet-shaped nanostructure. The wavelength position of the resonance peak of the nanocomposite structure will redshift as the size of the sheet-shaped nanostructure increases. According to the wavelength of the incident excitation light source, a nanocomposite structure matching its wavelength can be prepared. The band range that can be regulated by the resonance peak of the nanocomposite structure covers the ultraviolet to near-infrared band, which is wider than the band range of a single nanostructure. In order to reduce the interference of the analyte fluorescence signal on the Raman spectrum and improve the sensitivity of Raman spectroscopy detection, the near-infrared band is usually selected as the incident excitation light source. At this time, the wide resonance peak nanocomposite structure that can be adjusted to the near-infrared band has a more unique advantage.

[0006] The present invention provides a wide-band, multi-composite mechanism-based surface enhanced Raman scattering substrate, comprising a substrate and a nanocomposite structure randomly distributed on the substrate, wherein the nanocomposite structure comprises a rod-shaped nanostructure and two sheet-shaped nanostructures, wherein the rod-shaped nanostructure is sandwiched between the two sheet-shaped nanostructures and connected to the two sheet-shaped nanostructures.

[0007] Furthermore, the substrate material may be silicon wafer or glass material to facilitate post-processing of the Raman spectrum signal of the detected object.

[0008] Furthermore, the sheet-like nanostructure is preferably an isosceles triangle structure, and the rod-like nanostructure is sandwiched between two sheet-like nanostructures and connected to the bottom edges of the two isosceles triangle sheet-like nanostructures.

[0009] Furthermore, the diameter of the rod-like nanostructure is equal to the thickness of the sheet-like nanostructure. The length of the rod-like nanostructure is 40nm-40μm, the diameter is 5nm-500nm, the thickness of the sheet-like nanostructure is 5nm-500nm, and the side length of the two waists of the sheet-like nanostructure is 20nm-30μm.

[0010] Furthermore, the rod-shaped nanostructure and the sheet-shaped nanostructure are both made of precious metal materials such as gold, silver, and copper, and the materials of the rod-shaped nanostructure and the sheet-shaped nanostructure can be the same or different. The shapes and sizes of the two sheet-shaped nanostructures can be the same or different.

[0011] Furthermore, when the wide-band, multi-composite mechanism-based surface-enhanced Raman scattering substrate is used for material detection and analysis, the molecules of the object to be detected are covered on the substrate, and when the excitation light source is incident, local resonance enhancement is generated on the surface of the rod-shaped nanostructure and the sheet-shaped nanostructure, and local surface plasmons are formed on the surface of the nanocomposite structure, which interact with the molecules of the object to be detected to generate Raman signals; the molecules of the object to be detected are selected from environmental pollutant molecules, food harmful substance molecules or organic dye molecules with obvious Raman spectral characteristics; the excitation light source is selected from purple light, green light, red light or near-infrared light.

[0012] Furthermore, the present invention can regulate the resonance peak enhancement band range of the surface enhanced Raman scattering substrate in the range of ultraviolet light to near-infrared light by adjusting the length and diameter of the rod-like nanostructures and / or the side length and thickness of the sheet-like nanostructures, thereby meeting the needs of Raman excitation light sources with different wavelengths.

[0013] The present invention has the following beneficial effects:

[0014] The present invention solves the problem of low sensitivity of surface enhanced Raman scattering substrate reported in the past. The nanocomposite structure in the provided surface enhanced Raman scattering substrate is composed of a noble metal rod-shaped nanostructure and two sheet-shaped nanostructures. Local fields are formed on the surfaces of the rod-shaped nanostructure and the sheet-shaped nanostructure. The rod-shaped nanostructure has multiple peaks, and the sheet-shaped nanostructure has only one peak. By regulating the size of the sheet-shaped nanostructure, as long as the peak of the sheet-shaped nanostructure coincides with a peak of the rod-shaped nanostructure, after the two form a nanocomposite structure, under the action of the composite mechanism principle, the local field on its surface will be nonlinearly enhanced. Therefore, the surface enhanced Raman scattering substrate of the present invention has a higher surface enhanced Raman scattering enhancement ability. Under the best composite mechanism, the obtained resonance enhancement value is 10,000 times that of a single rod-shaped nanostructure or a sheet-shaped nanostructure, thereby effectively improving the detection sensitivity of the Raman spectrum.

[0015] The present invention also solves the problem of narrow range of surface enhanced Raman scattering substrate resonance enhancement band reported in the past. By adjusting the size and position of the rod-shaped nanostructure and the sheet-shaped nanostructure, the range of the surface enhanced Raman scattering substrate resonance enhancement band can be regulated in the ultraviolet to near-infrared range to meet the needs of Raman excitation light sources with different wavelengths. More importantly, when matching the long-wavelength excitation light source, selecting a longer-wavelength excitation light source can avoid the interference of the analyte fluorescence signal, which can not only further improve the sensitivity of Raman spectrum detection, but also be more conducive to the post-processing of the surface enhanced Raman scattering spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a schematic structural diagram of the surface enhanced Raman scattering substrate of the present invention.

[0017] Figure 2 Schematic diagram of the nanocomposite structure on the surface-enhanced Raman scattering substrate.

[0018] Figure 3 Schematic diagram of a series of nanocomposite structures with different size characteristics.

[0019] Figure 4 These are the resonance peaks formed by various nanostructures, where (a) is a plurality of resonance peaks formed by rod-like nanostructures, (b) is a single resonance peak formed by sheet-like nanostructures, and (c) is a resonance peak formed by nanocomposite structures.

[0020] Figure 5 This is the Raman spectrum of the Rhodamine 6G molecule in the application example.

[0021] Figure 6 It is a schematic diagram of the process of preparing a noble metal layer on a silicon wafer substrate by physical photolithography.

[0022] Among them, 1-substrate, 2-nanocomposite structure, 3-rod-shaped nanostructure, 4-sheet nanostructure, 5-molecules to be tested, 6-excitation light source, 7-surface plasmon signal, 8-Raman signal. DETAILED DESCRIPTION

[0023] In order to better understand the content of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings. The following embodiments are implemented based on the technology of the present invention, and detailed implementation methods and operating steps are given, but the protection scope of the present invention is not limited to the following embodiments.

[0024] like Figure 1 and Figure 2 As shown, the present invention provides a wide-band, multi-composite mechanism-based surface enhanced Raman scattering substrate comprising a substrate and a nanocomposite structure, wherein the substrate is made of a silicon wafer or glass material with a simple Raman spectrum structure to facilitate post-processing of the Raman spectrum signal of the detected object. The nanocomposite structure is randomly distributed on the substrate.

[0025] The nanocomposite structure includes a rod-shaped nanostructure and two isosceles triangle sheet-shaped nanostructures, the rod-shaped nanostructure is sandwiched between the two sheet-shaped nanostructures and connected to the bottom edges of the two isosceles triangle sheet-shaped nanostructures, the diameter of the rod-shaped nanostructure is equal to the thickness of the sheet-shaped nanostructure, and the rod-shaped nanostructure and the two isosceles triangle sheet-shaped nanostructures grow together to form the nanocomposite structure, such as Figure 2 shown.

[0026] In one embodiment, the length of the rod-like nanostructure is between 40nm-40μm, the diameter is between 5nm-500nm, the thickness of the sheet-like nanostructure is between 5nm-500nm, and the side length of the two waists of the sheet-like nanostructure is between 20nm-30μm.

[0027] The rod-shaped nanostructures and the sheet-shaped nanostructures are both made of gold, silver or copper noble metal materials, and the rod-shaped nanostructures and the sheet-shaped nanostructures can be made of the same material or different materials. In a group of nanocomposite structures, the shapes and sizes of the two sheet-shaped nanostructures can be the same or different.

[0028] like Figure 1 As shown, when the substrate is used for material detection and analysis, the molecules of the object to be detected are covered on the substrate. When the excitation light source is incident, local resonance enhancement characteristics will be generated on the surface of the rod-shaped nanostructure and the sheet-shaped nanostructure, and local surface plasmons will be formed on the surface of the nanocomposite structure, which will interact with the molecules of the object to be detected, thereby generating Raman signals. The molecules of the object to be detected can be environmental pollutant molecules, food harmful molecules or organic dye molecules with obvious Raman spectral characteristics, such as: cypermethrin (organochlorine insecticide), melamine, malachite green, rhodamine 6G, etc. The excitation light source can be purple light, green light, red light or near-infrared light.

[0029] The local field enhancement effect of the nanocomposite structure formed by a rod-like nanostructure and two sheet-like nanostructures is much greater than that of a single rod-like nanostructure or two sheet-like structures. By adjusting the length and diameter of the rod-like nanostructure and / or the side length and thickness of the sheet-like nanostructure, the resonance peak enhancement band range of the surface-enhanced Raman scattering substrate can be regulated in the range of ultraviolet light to near-infrared light to meet the needs of Raman excitation light sources with different wavelengths. More importantly, when matching the long-wavelength excitation light source, the interference of the analyte fluorescence signal can be avoided, which can not only further improve the sensitivity of Raman spectroscopy detection, but also be more conducive to the post-processing of the surface-enhanced Raman scattering spectrum.

[0030] according to Figure 4, the rod-like nanostructure has multiple peaks, and the range of the resonance enhancement band of the surface-enhanced Raman scattering substrate can be regulated in the range of ultraviolet light to near-infrared light to meet the needs of Raman excitation light sources of different wavelengths. The sheet-like nanostructure has only one peak. By regulating the size of the sheet-like nanostructure, as long as the peak of the sheet-like nanostructure matches the peak of the rod-like nanostructure, when the two form a nanocomposite structure, under the action of the composite mechanism principle, the local field on the surface of the nanocomposite structure will be nonlinearly enhanced. Therefore, the surface-enhanced Raman scattering substrate of the present invention has a wider band range and a higher surface-enhanced Raman scattering enhancement ability. Under the best composite mechanism, the obtained resonance enhancement value is 10,000 times that of a single rod-like nanostructure or a sheet-like nanostructure, thereby improving the sensitivity of Raman spectroscopy detection.

[0031] The nanocomposite structure of the present invention is etched on the substrate by the existing physical photolithography process, or deposited on the substrate by the existing chemical synthesis method. The following example introduces the process of the existing physical photolithography preparation process:

[0032] like Figure 6 As shown, the physical preparation process mainly includes (a) spin coating of photoresist, (b) exposure, (c) electron beam evaporation and (d) stripping.

[0033] (a) Spin coating of photoresist: In order to improve the adhesion of the photoresist, the substrate silicon wafer is first ultrasonically cleaned and blown dry with acetone, ethanol and deionized water in sequence to remove oil, particulate dust and other impurities on the silicon wafer. The silicon wafer is then heated on a heating table at 80°C for 5 min. Then, the photoresist is spin coated on the silicon wafer using a spin coater (3000 rpm, 45 s). Finally, the photoresist coating is dried.

[0034] (b) Exposure: The photoresist on the spin-coated substrate is selectively irradiated with ultraviolet light, and the photosensitizer in the photoresist changes. Then, the photoresist is placed in a corresponding developer for dissolution, and the desired pattern morphology can be obtained. In this step, the pattern of the nanocomposite structure of the present invention can be selectively irradiated to obtain the pattern morphology of the nanocomposite structure.

[0035] (c) Electron beam evaporation: The electron beam evaporation coating equipment is used to carry out precious metal coating process on the substrate after development. The thickness of the film can be precisely controlled by the current value and the evaporation time. The precious metal coating can be obtained on the silicon wafer through coating.

[0036] (d) Stripping: Use a stripping solution to remove the remaining photoresist film on the silicon wafer substrate, and at the same time, strip off the precious metal coating on the photoresist film. Finally, only the precious metal layer with a nanocomposite structure pattern remains on the silicon wafer substrate, thus obtaining a wide-band, multi-composite mechanism-based surface-enhanced Raman scattering substrate.

[0037] The present invention is further described below with specific embodiments and application examples:

[0038] Example 1

[0039] The nanocomposite structure includes a rod-shaped nanostructure and two sheet-shaped nanostructures. The rod-shaped nanostructure has a length of 100nm and a diameter of 8nm. The sheet-shaped nanostructure is an isosceles triangle with a thickness of 8nm. The vertex angle of the isosceles triangle sheet-shaped nanostructure is 80°, and the side length of the waist is 40nm. The two sheet-shaped nanostructures have the same size. The resonance peak of the nanocomposite structure prepared based on the above parameters is in the near-ultraviolet band. The nanocomposite structures are randomly distributed on the silicon wafer substrate. The materials of the rod-shaped nanostructure and the sheet-shaped nanostructure can be selected from precious metal materials such as gold, silver, and copper. The surface enhanced Raman scattering substrate is suitable for selecting ultraviolet light as the excitation light source.

[0040] Example 2

[0041] The nanocomposite structure includes a rod-shaped nanostructure and two sheet-shaped nanostructures. The rod-shaped nanostructure has a length of 200nm and a diameter of 12nm. The two sheet-shaped nanostructures of different sizes are both isosceles triangles. One isosceles triangle sheet-shaped nanostructure has a thickness of 12nm, a vertex angle of 100°, and a waist side length of 70nm. The other isosceles triangle sheet-shaped nanostructure has a thickness of 12nm, a vertex angle of 100°, and a waist side length of 62nm. The resonance peak of the nanocomposite structure prepared based on the above parameters is near 530nm. The nanocomposite structure is randomly distributed on the silicon wafer substrate. The rod-shaped nanostructure and the sheet-shaped nanostructure can be made of gold, silver, and copper precious metal materials. The surface enhanced Raman scattering substrate is suitable for selecting green light as the excitation light source.

[0042] Example 3

[0043] The nanocomposite structure includes a rod-shaped nanostructure and two sheet-shaped nanostructures. The rod-shaped nanostructure has a length of 500nm and a diameter of 20nm. The sheet-shaped nanostructure is an isosceles triangle with a thickness of 20nm. The vertex angle of the isosceles triangle sheet-shaped nanostructure is 120°, and the side length of the waist is 120nm. The two sheet-shaped nanostructures have the same size. The resonance peak of the nanocomposite structure prepared based on the above parameters is near 650nm. The nanocomposite structures are randomly distributed on the silicon wafer substrate. The materials of the rod-shaped nanostructure and the sheet-shaped nanostructure can be selected from gold, silver, and copper precious metal materials. The surface enhanced Raman scattering substrate is suitable for selecting red light as the excitation light source.

[0044] Example 4

[0045] The nanocomposite structure includes a rod-shaped nanostructure and two sheet-shaped nanostructures. The rod-shaped nanostructure has a length of 1.2 μm and a diameter of 90 nm. The sheet-shaped nanostructure is an isosceles triangle with a thickness of 90 nm. The vertex angle of the isosceles triangle sheet-shaped nanostructure is 70°, and the side length of the waist is 500 nm. The two sheet-shaped nanostructures have the same size. The resonance peak of the nanocomposite structure prepared based on the above parameters is around 950 nm. The nanocomposite structures are randomly distributed on the silicon wafer substrate. The materials of the rod-shaped nanostructure and the sheet-shaped nanostructure can be selected from precious metal materials such as gold, silver, and copper. The surface enhanced Raman scattering substrate is suitable for selecting infrared light as the excitation light source.

[0046] Application Example 1

[0047] The substrate structure of Example 3 is used to detect the pollutant organic aromatic dye molecule rhodamine 6G. Since the fluorescence peak wavelength of rhodamine 6G is around 560nm, in order to avoid the interference of its fluorescence signal, it is necessary to select red light with a longer wavelength as the excitation light source for Raman detection. The specific method is: first prepare 20ml of 10 -17 mol / L of Rhodamine 6G methanol solution was stirred vigorously for 5 minutes to completely dissolve Rhodamine 6G. A 1mL pipette was used to take the Rhodamine 6G methanol solution and drip it onto the surface enhanced Raman scattering substrate prepared with the nanocomposite structure. Then it was transferred to a 40℃ heating table and heated for 8 minutes for drying. Finally, red light was used as the excitation light source to test the Raman signal, and the collected Raman spectrum data was processed. The Raman spectrum of the Rhodamine 6G molecule is shown in the figure below. Figure 5 The nanocomposite surface enhanced Raman scattering substrate proposed in the present invention can quickly detect concentrations as low as 10 due to the composite resonance enhancement characteristics of the rod-like nanostructure and the sheet-like nanostructure. -17 mol / L of Rhodamine 6G molecules has a significant Raman enhancement effect and a lower detection limit than existing technologies.

[0048] The above application example is only a specific application of the present application. The present invention can also be used to detect pollutants such as cypermethrin (organochlorine insecticide), melamine, malachite green, etc., which will not be described one by one.

[0049] The above is only an embodiment of the present invention, and does not limit the present invention in any form. The present invention can also have other forms of embodiments according to the above structures and functions, which are not listed one by one. Therefore, any simple modification, equivalent change and modification made by any technician familiar with the profession to the above embodiment according to the technical essence of the present invention without departing from the scope of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A wide-band, multi-composite mechanism surface-enhanced Raman scattering substrate, characterized in that The invention comprises a substrate and a nanocomposite structure randomly distributed on the substrate, wherein the nanocomposite structure comprises a rod-shaped nanostructure and two isosceles triangle sheet-shaped nanostructures, wherein the rod-shaped nanostructure is sandwiched between the two isosceles triangle sheet-shaped nanostructures and grows together with the bottom edges of the two isosceles triangle sheet-shaped nanostructures, the diameter of the rod-shaped nanostructure is equal to the thickness of the sheet-shaped nanostructure, and the rod-shaped nanostructure and the sheet-shaped nanostructure are both made of gold, silver or copper.

2. The wide-band, multi-composite mechanism surface-enhanced Raman scattering substrate according to claim 1, characterized in that The substrate is made of silicon wafer or glass material.

3. The wide-band, multi-composite mechanism surface-enhanced Raman scattering substrate according to claim 1, characterized in that The length of the rod-like nanostructure is 40 nm-40 μm, the diameter is 5 nm-500 nm, the thickness of the sheet-like nanostructure is 5 nm-500 nm, and the side length of the two waists of the sheet-like nanostructure is 20 nm-30 μm.

4. The surface enhanced Raman scattering substrate with a wide band and multi-composite mechanism as claimed in any one of claims 1 to 3, characterized in that The rod-shaped nanostructure and the plate-shaped nanostructure are made of the same or different materials.

5. The surface enhanced Raman scattering substrate with a wide band and multi-composite mechanism as claimed in any one of claims 1 to 3, characterized in that The shapes and sizes of the two sheet-like nanostructures are the same or different.

6. Application of the wide-band, multi-composite mechanism-based surface-enhanced Raman scattering substrate as claimed in claim 1 in the detection of deltamethrin, melamine, malachite green and rhodamine 6G.

7. The use according to claim 6, characterized in that The excitation light source is purple light, green light, red light or near infrared light.

8. The use according to claim 6, characterized in that Red light was used as the excitation light source when Rhodamine 6G was detected by surface enhanced Raman scattering substrate.

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