Thiol and graphene-modified surface-enhanced Raman scattering composite substrates, their preparation methods and applications

Abstract

This invention relates to the field of surface-enhanced Raman spectroscopy (SERS) detection technology, and discloses a thiol and graphene-modified SERS composite substrate, its preparation method, and its applications. The composite substrate comprises a substrate, silver nanowires attached to the substrate, a graphene layer, gold nanospheres, and thiols modified on the graphene layer and gold nanospheres. This composite substrate combines gold nanospheres, graphene, and silver nanowires to form a three-dimensional nanostructure of silver nanowires-graphene-gold nanospheres, effectively improving its detection performance. Furthermore, by modifying the three-dimensional nanostructure of silver nanowires-graphene-gold nanospheres with thiol, the resulting composite substrate exhibits high sensitivity for the detection of substances (e.g., organic pollutants). In addition, this invention provides a method for preparing the thiol and graphene-modified SERS composite substrate, which involves solution evaporation and self-assembly. This method is simple and rapid, does not involve expensive instruments, and the solid substrate facilitates storage and handling, making it easy to further promote and apply.

Description

Technical Field

[0001] This invention relates to the field of surface-enhanced Raman spectroscopy, specifically to a thiol and graphene-modified surface-enhanced Raman scattering composite substrate, its preparation method, and its application. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are products of the incomplete combustion of fossil fuels or carbon-containing materials such as wood and tobacco. They are mostly compounds containing two or more benzene rings in a fused ring configuration. As a class of persistent organic pollutants (POPs), PAHs have the following characteristics: 1. Numerous types, including hundreds of species such as naphthalene, anthracene, phenanthrene, pyrene, and their derivatives; 2. Wide distribution, commonly found in the atmosphere, soil, water bodies, and various solid pollutants; 3. Long persistence and difficulty in degradation; 4. Strong mutagenic and carcinogenic properties, making them significant environmental and food pollutants, posing a great threat to the deteriorating ecological environment and human health. Currently, the main methods for detecting PAHs include capillary electrophoresis, gas chromatography-mass spectrometry, and fluorescence spectroscopy. However, these methods involve complex sample pretreatment steps, cumbersome operations, and are mostly performed under laboratory conditions. Therefore, establishing a rapid, real-time, and simple detection and analysis technology for polycyclic aromatic hydrocarbons is of great practical significance for the sustainable development of the environment and human survival.

[0003] Surface-enhanced Raman scattering (SERS) is an emerging detection method with advantages such as high sensitivity, rich chemical fingerprint information, simple operation, and in-situ detection. The enhancement effect of the SERS substrate depends on the electromagnetic field enhancement regions ("hot spots") on the surface of the structure; the greater the density and intensity of the "hot spots," the more significant the enhancement effect of the SERS substrate. Therefore, fabricating three-dimensional nanostructures and increasing the density and intensity of electromagnetic field enhancement regions within them is increasingly becoming a preferred choice. Currently, there are some reports on the detection of polycyclic aromatic hydrocarbons (PAHs) using SERS technology.

[0004] CN102380984A discloses a surface-enhanced Raman spectroscopy (SERS) substrate suitable for detecting polycyclic aromatic hydrocarbons (PAHs) in seawater. Specifically, it discloses the use of trimethoxysilane-functionalized quartz sheets, immersing the functionalized quartz sheets in a gold sol to obtain a gold sol film, and then modifying the gold sol film with 25,27-dimercaptoacetic acid-26,28-dihydroxy-4-tert-butylcalixarene. The time spent in the 25,27-dimercaptoacetic acid-26,28-dihydroxy-4-tert-butylcalixarene methanol solution is adjusted to obtain a SERS substrate with optimal enhancement effect.

[0005] CN103257063A discloses a reagent for detecting polycyclic aromatic hydrocarbons in water. The reagent is composed of reagent A and reagent B, wherein reagent A is an aqueous solution of graphene / nano-noble metal composite and reagent B is a surfactant solution.

[0006] The above-mentioned drawbacks of surface-enhanced Raman scattering composite substrates for detecting polycyclic aromatic hydrocarbons include complex preparation processes, substrates being mostly liquids that are inconvenient to store and use, and the adsorption of polycyclic aromatic hydrocarbons mostly through single non-covalent bond forces. Therefore, there is a need to find a surface-enhanced Raman scattering composite substrate that is simple to prepare and has high detection sensitivity. Summary of the Invention

[0007] The purpose of this invention is to overcome the technical problems of existing technologies, such as complex preparation processes, mostly liquid substrates, inconvenience in storage and use, and adsorption of polycyclic aromatic hydrocarbons mostly through single non-covalent bond forces, and to provide a thiol and graphene modified surface-enhanced Raman scattering composite substrate (gold / graphene / silver nanocomposite substrate), its preparation method and application.

[0008] To achieve the above objectives, the first aspect of the present invention provides a surface-enhanced Raman scattering composite substrate modified with thiol and graphene, the composite substrate comprising a substrate, silver nanowires attached to the substrate, a graphene layer, gold nanospheres, and thiols modified on the graphene layer and gold nanospheres.

[0009] A second aspect of the present invention provides a method for preparing a thiol and graphene-modified surface-enhanced Raman scattering composite substrate, the method comprising the following steps:

[0010] (1) Silver nanowires, graphene layers and gold nanospheres are attached to the surface of a substrate to obtain an active substrate;

[0011] (2) The active substrate obtained in step (1) is modified with thiol to obtain a surface-enhanced Raman scattering composite substrate modified with thiol and graphene.

[0012] The third aspect of the present invention provides an application of the composite substrate described in the first aspect or the composite substrate prepared by the method described in the second aspect above in the detection of hydrophobic molecules, particularly in the detection of polycyclic aromatic hydrocarbons.

[0013] Compared with existing technologies, the thiol and graphene-modified surface-enhanced Raman scattering (SERS) composite substrate provided by this invention combines gold nanospheres, graphene, and silver nanowires to form a three-dimensional nanostructure of silver nanowires-graphene-gold nanospheres. The graphene layer enhances the detection sensitivity for polycyclic aromatic hydrocarbons (PAHs). Furthermore, by modifying the three-dimensional nanostructure of silver nanowires-graphene-gold nanospheres (the active substrate) with thiol, the composite substrate of this invention can effectively adsorb PAHs onto the surface of the SERS substrate, further improving the detection effect of PAHs. In addition, this invention also provides a method for preparing the thiol and graphene-modified SERS composite substrate, which involves solution evaporation self-assembly (e.g., drop coating, immersion), a simple and rapid method that does not involve expensive equipment, facilitating further promotion and application. Attached Figure Description

[0014] Figure 1 These are scanning electron microscope (SEM) images of different substances attached to the substrate surface. Among them, (A) is a scanning electron microscope image of silver nanowires attached to the substrate surface according to a specific embodiment of the present invention, (B) is a scanning electron microscope image of silver nanowire-graphene layer attached to the substrate surface according to a specific embodiment of the present invention, and (C) is a scanning electron microscope image of silver nanowire-graphene layer-gold nanospheres attached to the substrate surface according to a specific embodiment of the present invention.

[0015] Figure 2 The composite substrates prepared in Examples 1, 2, 3, and 4 with different graphene contents are 10 -3 Surface-enhanced Raman signal spectrum obtained by detecting mol / L pyrene;

[0016] Figure 3 The composite substrates prepared in Examples 1, 5, and 6 with different gold nanosphere contents are 10 -3 Surface-enhanced Raman signal spectrum obtained by detecting mol / L pyrene;

[0017] Figure 4 Different thiol molecules were modified on the substrate. The composite substrates prepared in Examples 1, 7, and 8 were 10 -3 Surface-enhanced Raman signal spectrum obtained by detecting mol / L pyrene;

[0018] Figure 5 The composite substrates prepared in Examples 1 and 9-12 are 10 -3 Surface-enhanced Raman signal spectrum obtained by detecting mol / L pyrene;

[0019] Figure 6 The 590cm obtained from test examples 1 and 9-12 is... 1 The curve showing the functional relationship between the intensity of the characteristic peak and the concentration;

[0020] Figure 7 The composite substrates in the three comparative examples are 10 -3 Surface-enhanced Raman signal spectrum obtained by detecting mol / L pyrene. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The first aspect of the present invention provides a surface-enhanced Raman scattering composite substrate modified with thiol and graphene, the composite substrate comprising a substrate, silver nanowires attached to the substrate, a graphene layer, gold nanospheres, and thiols modified on the graphene layer and gold nanospheres.

[0023] According to some embodiments of the present invention, the adhesion rate of the silver nanowires on the substrate can be 50-90%, preferably 70-80%; the adhesion rate of the gold nanospheres on the graphene layer can be 40-80%, preferably 50-70%. Herein, "adhesion rate" is calculated based on scanning electron microscope images, determining the coverage rate of the silver nanowires on the substrate and the coverage rate of the gold nanospheres on both the silver nanowires and the graphene substrate.

[0024] According to some embodiments of the present invention, in order to make the prepared composite substrate have better performance, the present invention has certain requirements on the shape and size of the silver nanowires. For example, the silver nanowires can be cylindrical, with a diameter of 10-30 nm, preferably 15-25 nm; and a length of 20-40 μm, preferably 25-35 μm.

[0025] According to some embodiments of the present invention, the content of the silver nanowires relative to the substrate square centimeter can be 0.02-0.21 mg, preferably 0.05-0.12 mg (0.05 mg, 0.06 mg, 0.07 mg, 0.08 mg, 0.09 mg, 0.1 mg, 0.11 mg, 0.12 mg or any value between the above values).

[0026] According to some embodiments of the present invention, in order to make the prepared composite substrate have better performance, the present invention has certain requirements on the diameter of the gold nanospheres. The diameter of the gold nanospheres can be 10-40 nm, preferably 20-30 nm.

[0027] According to some embodiments of the present invention, the content of the gold nanospheres relative to each square centimeter of substrate can be 0.001-0.24 mg, preferably 0.009-0.075 mg (0.009 mg, 0.01 mg, 0.015 mg, 0.02 mg, 0.025 mg, 0.03 mg, 0.035 mg, 0.04 mg, 0.045 mg, 0.05 mg, 0.055 mg, 0.06 mg, 0.065 mg, 0.07 mg, 0.075 mg or any value between the above values).

[0028] According to some embodiments of the present invention, the content of the graphene layer relative to each square centimeter of substrate can be 0.00005-0.024 mg, preferably 0.001-0.012 mg (0.001 mg, 0.002 mg, 0.0003 mg, 0.0004 mg, 0.0005 mg, 0.0006 mg, 0.0007 mg, 0.008 mg, 0.009 mg, 0.01 mg, 0.011 mg, 0.012 mg or any value between the above values).

[0029] According to some embodiments of the present invention, the thiol is a straight-chain alkyl thiol, which may be selected from C3-C12 thiols (propanethiol, butanethiol, pentathiol, hexanethiol, heptathiol, ..., dodecathiol), preferably selected from C3-C6 thiols.

[0030] The present invention does not have any special requirements on the type of substrate. Conventional surface-enhanced Raman substrates of the present invention can be used. For example, the substrate can be selected from glass substrates or semiconductor substrates.

[0031] In this invention, there are no special requirements for the thickness of the substrate, as long as it meets the requirements of this invention. In order to obtain better results, the thickness of the substrate is 0.2-2cm, preferably 0.5-1cm.

[0032] According to a particularly preferred embodiment, the silver nanowires have an adhesion rate of 70-75% to the substrate; the gold nanospheres have an adhesion rate of 60-70% to the silver nanowires. The silver nanowires are cylindrical with a diameter of 25-35 nm and a length of 18-22 μm. The content of the silver nanowires is 0.07-0.09 mg per square centimeter of substrate. The gold nanospheres have a diameter of 22-28 nm. The content of the gold nanospheres is 0.015-0.04 mg per square centimeter of substrate. The content of the graphene layer is 0.002-0.005 mg per square centimeter of substrate. The thiol is a straight-chain alkyl thiol, a C3-C5 thiol.

[0033] A second aspect of the present invention provides a method for preparing a thiol and graphene-modified surface-enhanced Raman scattering composite substrate, the method comprising the following steps:

[0034] (1) Silver nanowires, graphene layers and gold nanospheres are attached to the surface of a substrate to obtain an active substrate;

[0035] (2) The active substrate obtained in step (1) is modified with thiol to obtain a surface-enhanced Raman scattering composite substrate modified with thiol and graphene.

[0036] According to some embodiments of the present invention, in step (1), the method of attaching silver nanowires, graphene layer and gold nanospheres on the substrate surface is to attach silver nanowires, graphene layer and gold nanospheres sequentially on the substrate surface.

[0037] In this invention, there are no particular limitations on the method of attaching silver nanowires and gold nanospheres; coating can be performed in the form of a solution.

[0038] Preferably, the silver nanowires are attached by using a silver nanowire sol for the first drop coating;

[0039] Preferably, the graphene layer is attached by using a graphene solution for a second drop coating;

[0040] Preferably, the gold nanospheres are attached by using a gold nanosphere sol for a third drop coating.

[0041] According to some embodiments of the present invention, the concentration of the silver nanowire sol can be 0.5-3 mg / mL, preferably 1-2 mg / mL.

[0042] According to some embodiments of the present invention, the silver nanowires are cylindrical with a diameter of 10-30 nm, preferably 15-25 nm, and a length of 20-40 μm, preferably 25-35 μm.

[0043] In this invention, the silver nanowire sol can be prepared by the following steps:

[0044] In the presence of a first solvent, polyvinylpyrrolidone is contacted with silver nitrate to obtain a mixture, which is then subjected to sealed heating treatment to obtain a suspension; subsequently, it is obtained by centrifugation.

[0045] The first solvent can be water.

[0046] The contact conditions include: a temperature of 20-40°C, preferably 25-35°C; a time of 10-50 min, preferably 20-40 min; a rotation speed of 200-500 rpm, preferably 300-400 rpm; wherein, relative to each gram of silver nitrate, the amount of polyvinylpyrrolidone used is 5-30 g, preferably 15-20 g; and relative to each milligram of silver nitrate, the amount of the first solvent used is 0.5-5 mL, preferably 1-3 mL.

[0047] The conditions for the sealing heat treatment include: a temperature of 120-200℃, preferably 150-180℃; and a time of 2-10 hours, preferably 5-8 hours.

[0048] The centrifugation conditions include: a rotation speed of 2000-6000 rpm, preferably 3000-5000 rpm, and a time of 2-20 min, preferably 5-10 min. The centrifugation step can be repeated 2-5 times.

[0049] In this invention, the silver nanowire sol is preferably prepared according to the following steps:

[0050] The first solvent is mixed with polyvinylpyrrolidone and stirred at room temperature (25-30℃) for 20-40 min to obtain a polyvinylpyrrolidone solution. Then, AgNO3 is added to the polyvinylpyrrolidone solution and stirred at 3000-4000 rpm for 5-15 min to obtain a mixture. The mixture is then sealed and heated at 150-180℃ for 5-8 hours to obtain a suspension containing silver nanoparticles. Finally, the suspension is centrifuged at 3500-4500 rpm for 3-8 min, repeated 2-5 times, to obtain a silver nanowire sol. The first solvent is preferably water.

[0051] According to some embodiments of the present invention, the conditions for the first drop coating may include: a temperature of 20-100°C, preferably 30-80°C (30°C, 40°C, 50°C, 60°C, 70°C, 80°C or any value between the above values).

[0052] The present invention does not have a particular limitation on the time of the first drop coating, as long as the solvent of the silver nanowire sol can be completely evaporated and the silver nanowires can be attached to the substrate surface.

[0053] In this invention, the silver nanowires are adsorbed onto the substrate surface under the action of capillary force and gravity.

[0054] According to some embodiments of the present invention, the amount of the silver nanowire sol can be 40-70 μL, preferably 50-60 μL, relative to the substrate per square centimeter.

[0055] According to some embodiments of the present invention, the amount of silver nanowires used is such that 0.02-0.21 mg of silver nanowires are attached to the substrate surface per square centimeter, preferably 0.05-0.12 mg of silver nanowires.

[0056] According to some embodiments of the present invention, the conditions for the second drop coating may include a temperature of 10-40°C, preferably 15-30°C.

[0057] According to some embodiments of the present invention, the concentration of the graphene solution can be 0.01-0.8 mg / mL, preferably 0.1-0.6 mg / mL.

[0058] According to some embodiments of the present invention, the amount of graphene used is such that the weight of the graphene layer attached to the substrate surface per square centimeter is 0.00005-0.024 mg, preferably 0.001-0.012 mg.

[0059] According to a preferred embodiment of the present invention, the amount of graphene solution used per square meter of glass substrate can be 5-30 μL, preferably 10-20 μL.

[0060] According to some embodiments of the present invention, the concentration of the gold nanosphere sol can be 0.1-2 mg / mL, preferably 0.3-1 mg / mL.

[0061] According to some embodiments of the present invention, the diameter of the gold nanospheres can be 10-40 nm, preferably 20-30 nm.

[0062] In this invention, the gold nanosphere sol can be prepared by the following method: sodium citrate is added to a boiling HAuCl4 solution for reaction, and the reaction solution is centrifuged after turning purple-red.

[0063] The HAuCl4 solution is obtained by mixing an aqueous solution of HAuCl4 with a second solvent; the concentration of the aqueous HAuCl4 solution is 0.01-0.05 mol / L, preferably 0.02-0.03 mol / L; and the mixture is heated to boiling. The amount of the second solvent used is 300-1000 mL, preferably 500-700 mL, relative to each mL of the aqueous HAuCl4 solution. The second solvent can be water.

[0064] Sodium citrate is preferably added to the boiling HAuCl4 solution in solution form, with a concentration of 0.01-0.05 mol / L, preferably 0.02-0.03 mol / L. The volume of sodium citrate solution used is 2-20 mL, preferably 5-10 mL, relative to each mL of the HAuCl4 aqueous solution.

[0065] In the preparation of gold nanosphere sol, the reaction temperature is preferably 100℃; the reaction time is 10-50 min, preferably 20-40 min.

[0066] In this invention, the gold nanosphere sol is preferably prepared according to the following steps:

[0067] Mix the aqueous solution of HAuCl4 with deionized water and heat it in an oil bath at 120-150℃ until the system solution boils. Then mix it with the aqueous solution of sodium citrate and keep it at boiling temperature for 30 minutes until the system solution gradually turns purple-red. Then centrifuge the reaction solution at 3000-4000 rpm for 10-15 minutes to obtain gold nanosphere sol.

[0068] According to some embodiments of the present invention, the conditions for the third drop application may include: a temperature of 30-100°C, preferably 40-80°C.

[0069] The present invention does not have a particular limitation on the time of the third drop coating, as long as the solvent of the gold nanosphere sol can be completely evaporated and the gold nanospheres can be attached to the silver nanowires.

[0070] In this invention, the gold nanosphere sol is adsorbed onto the substrate under the action of capillary force and gravity.

[0071] According to some embodiments of the present invention, the amount of gold nanosphere sol used is such that 0.001-0.24 mg of gold nanospheres are attached to each square centimeter of substrate surface, preferably 0.009-0.075 mg of gold nanospheres.

[0072] According to some embodiments of the present invention, the amount of gold nanosphere sol used per square meter of substrate can be 10-30 μL, preferably 15-25 μL.

[0073] In this invention, to achieve better results, the number of third drop coatings is specified. Preferably, the third drop coating can be performed 1-4 times, more preferably 2-3 times. The next drop coating operation is performed only after the solvent of the previously added gold nanoparticle sol has completely evaporated.

[0074] According to some embodiments of the present invention, in step (2), the modification can be performed by immersing the active substrate in a thiol solution.

[0075] According to some embodiments of the present invention, the thiol is selected from C3-C12 thiols (propanethiol, butanethiol, pentathiol, hexanethiol, heptathiol, ..., dodecathiol), preferably selected from C3-C6 thiols.

[0076] In this invention, before obtaining the thiol and graphene-modified surface-enhanced Raman scattering composite substrate, residual thiol solution on the active substrate is removed using filter paper. Preferably, the active substrate soaked in the thiol solution is then soaked in a washing solvent (which can be repeated 3-4 times), and excess washing solvent and thiol on the surface are removed using filter paper. The washing solvent can be selected from at least one of ethanol, acetone, and ethyl acetate.

[0077] In this invention, the thiol solution can be at least one of an aqueous solution of thiol, an ethanol solution, an acetone solution, and an ethyl acetate solution, preferably an ethanol solution of thiol.

[0078] According to some embodiments of the present invention, the concentration of the thiol solution may be 10. -4 -10 -1 mol / L, preferably 10 -3 -10 -2 mol / L.

[0079] According to some embodiments of the present invention, the soaking conditions may include: a temperature of 15-35°C, preferably 20-25°C; and a time of 0.1-2 h, preferably 0.2-0.8 h.

[0080] In this invention, the substrate can be selected from a glass substrate or a semiconductor substrate. Preferably, the substrate can be pretreated as follows before attaching the silver nanowires: sequentially cleaned with piranha solution, acetone, ethanol, and deionized water, and then dried. There is no particular limitation on the amount of piranha solution, acetone, ethanol, and deionized water used for cleaning the substrate.

[0081] The third aspect of the present invention provides an application of the composite substrate described in the first aspect or the composite substrate prepared by the method described in the second aspect above in the detection of hydrophobic molecules, particularly in the detection of polycyclic aromatic hydrocarbons.

[0082] According to some embodiments of the present invention, the polycyclic aromatic hydrocarbon may be selected from at least one of naphthalene, anthracene, phenanthrene, pyrene and benzo[a]pyrene; preferably selected from pyrene and / or anthracene.

[0083] According to some embodiments of the present invention, the surface-enhanced Raman scattering composite substrate has a detection concentration of ≥10 for polycyclic aromatic hydrocarbons. -6mol / L.

[0084] The present invention will be described in detail below through embodiments.

[0085] In the following examples, all raw materials used are commercially available products.

[0086] This preparation example illustrates the preparation method of the silver nanowire sol of the present invention.

[0087] Preparation Example A

[0088] Add 0.3 g of polyvinylpyrrolidone (PVP, M) sequentially to a 250 mL single-necked flask. W =55000), 35 mL of deionized water, stirred at 350 rpm for 30 min at room temperature to obtain a clear solution of polyvinylpyrrolidone; then 0.017 g of AgNO3 was added to the polyvinylpyrrolidone solution, and stirred at 350 rpm for 10 min to obtain a mixture; then the mixture was transferred to a 50 mL hydrothermal reactor, sealed at 165 °C for 6 hours to obtain a suspension containing silver nanowires; the suspension was taken out into a 10 mL reaction flask, centrifuged at 4000 rpm for 5 min, the supernatant was aspirated, deionized water was added, and centrifugation was repeated twice to obtain a solution of silver nanowires (diameter 30 nm, length 20 μm) with a concentration of 1.5 mg / mL.

[0089] This preparation example illustrates the preparation method of the gold nanosphere sol of the present invention.

[0090] Preparation Example B

[0091] Add 0.25 mL of HAuCl4 aqueous solution (0.02 mol / L) and 150 mL of deionized water to a 250 mL single-necked flask. Heat the solution in an oil bath at 135 °C until it boils. After boiling for 10 min, add 2 mL of 0.02 mol / L sodium citrate solution. Then keep the solution at boiling for 30 min. The solution gradually turns purple-red. After that, centrifuge the solution at 3500 rpm for 13 min to prepare a gold nanosphere sol with a concentration of 0.8 mg / mL and a diameter of 25 nm.

[0092] Example 1

[0093] (1) 1cm 2A 5mm thick glass substrate was cleaned with 10mL of piranha solution (a mixture of concentrated sulfuric acid and 30% hydrogen peroxide in a 7:3 volume ratio), followed by cleaning with 20mL of acetone, 20mL of ethanol, and 20mL of deionized water, and finally dried with nitrogen to obtain a clean glass substrate. The glass substrate was then placed in a 50℃ oven, and a first drop of 55µL of 1.5mg / mL silver nanowire sol was applied to its surface. After the solvent evaporated, a substrate with silver nanowires attached was obtained (e.g., ...). Figure 1 A). A substrate with attached silver nanowires was placed at room temperature, and 15 μL of a 0.25 mg / mL aqueous solution of graphene oxide was dropped onto the surface of the silver nanowires. After the solvent completely evaporated, a substrate with attached graphene and silver nanospheres was obtained (e.g., ...). Figure 1 B); Then, the substrate with graphene and silver nanospheres attached was placed on a hot plate at 50°C. A third drop of 10 μL of 0.8 mg / mL gold nanosphere sol was applied to the surface of the substrate. After the solvent in the solution evaporated, the third drop was repeated twice to obtain the active substrate (e.g., ...). Figure 1 C).

[0094] (2) Prepare a concentration of 10 -3 An ethanol solution of propanethiol at mol / L was used to prepare the above active substrate at room temperature. -3 The active substrate was soaked in an ethanol solution of mol / L propanethiol for 30 min. Then, the soaked active substrate was removed, and the residual propanethiol ethanol solution on the surface of the active substrate was removed with filter paper. After that, it was placed in ethanol and shaken for 2 min. After that, the residual propanethiol and ethanol on the surface of the active substrate were removed with filter paper. Then, the active substrate was placed in the ethanol solution and shaken for 2 min again. The above steps (soaking in ethanol, shaking and removing residual propanethiol and ethanol on the surface) were repeated 3 times to remove the propanethiol that was not adsorbed on the surface of the active substrate, and the composite substrate was obtained, which was designated as S1 (see Table 2).

[0095] Examples 2-8

[0096] The procedure was carried out as in Example 1, except that Examples 2-8 varied one or more parameters, such as the concentration of the graphene solution, the number of third drop coatings (the number of drop coatings of the gold nanosphere sol), and the soaking time of the thiol solution, as detailed in Table 1. The final composite substrates obtained were S2-S8 (see Table 2).

[0097] Comparative Example 1

[0098] The procedure was carried out as described in Example 1, except that graphene was not added during the preparation of the composite substrate. The resulting composite substrate was designated D1 (see Table 2).

[0099] Comparative Example 2

[0100] The procedure was carried out as in Example 1, except that no gold nanospheres were attached during the preparation of the composite substrate. The resulting composite substrate was designated D2 (see Table 2).

[0101] Comparative Example 3

[0102] The procedure was carried out as in Example 1, except that thiol soaking was not used during the preparation of the composite substrate. The resulting composite substrate was designated D3 (see Table 2).

[0103] Table 1

[0104]

[0105] In Table 2, "Adhesion rate 1" is the coverage rate of silver nanowires on the substrate per unit area calculated based on the scanning electron microscope images of the substrate; "Adhesion rate 2" is the coverage rate of gold nanospheres on silver nanowires per unit area calculated based on the scanning electron microscope images of the substrate.

[0106] Among them, the content of silver nanowires is equal to the concentration of silver nanowire sol multiplied by the drop volume; the content of graphene is equal to the concentration of graphene solution multiplied by the drop volume; and the content of gold nanospheres is equal to the concentration of gold nanosphere sol multiplied by the drop volume.

[0107] Table 2

[0108]

[0109] Test Examples 1-8

[0110] The composite substrate obtained in the above examples was used to detect surface-enhanced Raman signals of polycyclic aromatic hydrocarbons (pyrene).

[0111] Test conditions: The test was conducted using a Horiba Xplus microconfocal Raman spectrometer (manufacturer: Horiba), with a laser wavelength of 785nm, a power of 10mW, a filter transmittance of 1%, an integration time of 20s, and 2 integration cycles.

[0112] Test procedure: Add 10 μL of 10 -3 A mol / L pyrene ethanol solution was dropped onto the surface of composite substrates S1-S8. After the solution evaporated, the surface-enhanced Raman signal of pyrene was measured. The characteristic peaks of pyrene molecules were mainly at 401, 590, 1058, 1235, 1403, 1594, and 1623 cm⁻¹. -1 Select 590cm -1 To compare the intensity of the characteristic peak, the 590 cm⁻¹ intensity of pyrene on the S1-S8 composite substrates was recorded. -1 The intensity of the characteristic peak.

[0113] like Figure 2 At different graphene contents, pyrene was tested on S1, S2, S3, and S4 composite substrates, yielding a thickness of 590 cm⁻¹. -1 The intensities of the characteristic peaks were 9313, 5825, 6978, and 8175, respectively. These results show that S2 contains relatively little graphene, which can adsorb and chemically enhance a small amount of pyrene molecules, but the intensity is weak. In S3, the graphene content increases, improving both the chemical enhancement and adsorption effects, resulting in increased intensity. In S1, the graphene content continues to increase, and the intensity of pyrene molecules also continues to increase. In S4, the graphene content continues to increase, but the graphene layer becomes too thick, leading to a larger spacing between the gold nanospheres and silver nanowires, resulting in a decrease in the Raman signal intensity of pyrene molecules compared to S1.

[0114] like Figure 3 In different gold nanosphere contents, pyrene was tested on S1, S5, and S6 composite substrates and the result was 590 cm⁻¹. -1 The intensities of the characteristic peaks were 9313, 5085, and 9220, respectively. From the above results, it can be seen that in S5, the gold nanospheres were added only once, resulting in the lowest content and thus a weaker Raman signal; in S1, the gold nanospheres were added three times, increasing the content and enhancing the Raman signal; in S6, the gold nanospheres were added four times, further increasing the content, but the thickness of the gold nanospheres increased while the surface area in contact with pyrene remained unchanged, therefore the Raman signal intensity was basically the same as in S1.

[0115] like Figure 4 In 10 of propanethiol -3 Pyrene was immersed in ethanol solution at different times, and the 590 cm⁻¹ value was obtained by testing on S1, S7, and S8 composite substrates. -1 The intensities of the characteristic peaks were 9313, 4067, and 9165, respectively. In S7, the immersion time was relatively short, and the Raman signal was weak. In S1, the immersion time was increased, and the Raman signal was enhanced. In S8, the immersion time was further increased, but the Raman signal did not continue to increase, remaining basically the same as in S1.

[0116] The above experiments show that S1 is the substrate with the greatest Raman signal enhancement capability.

[0117] Test Example 9-12

[0118] The procedure was performed as in Test Example 1, except that the concentration of the pyrene ethanol solution was changed (10... -6 10 -5 10 -4 10 -2 The Raman signal intensity was obtained as follows (mol / L). Figure 5 As shown.

[0119] from Figure 5 It can be seen that as the concentration gradually decreases, the intensity of the characteristic peak also gradually decreases. The composite substrate S1 of Example 1 can achieve 10 -6 Qualitative detection of pyrene molecules at a concentration of mol / L.

[0120] The 590cm obtained from test examples 1 and 9-12 -1 The intensity of the characteristic peak is plotted on the ordinate, and the logarithm of the concentration on the abscissa, resulting in a functional relationship curve. From Figure 6 It can be seen that the intensity of this characteristic peak exhibits a good quadratic functional relationship with the logarithm of its concentration. Based on this mathematical relationship, for solutions of unknown concentration, after measuring 590 cm⁻¹... -1 After determining the intensity of the characteristic peak, combine Figure 6 This allows for the calculation of the solution's concentration, thus enabling the quantitative detection of pyrene molecules.

[0121] Therefore, the quantitative detection of polycyclic aromatic hydrocarbon molecules can be achieved by using the functional relationship curve between the intensity of the obtained Raman signal peak and the concentration of polycyclic aromatic hydrocarbons.

[0122] Test comparison

[0123] The procedure was performed as in Test Example 1, except that an ethanol solution of pyrene was added dropwise to the composite substrates prepared in Comparative Examples 1-3. After the solution evaporated, the surface-enhanced Raman signal of pyrene was measured to obtain the Raman signal intensity. Figure 7 D1, D2, and D3 are 4261, 3889, and 2555, respectively.

[0124] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of a thiol and graphene-modified surface-enhanced Raman scattering composite substrate in the detection of pyrene, characterized in that, The composite substrate includes a substrate, silver nanowires attached to the substrate, a graphene layer, gold nanospheres, and thiols modified on the graphene layer and gold nanospheres. The silver nanowires contain 0.02-0.21 mg of silver nanowires, 0.024-0.075 mg of gold nanospheres, 0.001-0.012 mg of graphene layers, and the thiol is propanethiol, relative to the substrate per square centimeter. The silver nanowires are cylindrical with a diameter of 10-30 nm and a length of 20-40 μm; the gold-sodium nanospheres have a diameter of 10-40 nm. The adhesion rate of the silver nanowires on the substrate is 50-90%; the adhesion rate of the gold nanospheres on the graphene layer is 40-80%. The method for preparing thiol and graphene-modified surface-enhanced Raman scattering composite substrates includes the following steps: (1) Silver nanowires, graphene layers and gold nanospheres are attached to the surface of a substrate to obtain an active substrate; (2) The active substrate obtained in step (1) is modified with thiol to obtain a surface-enhanced Raman scattering composite substrate modified with thiol and graphene. In step (2), the modification method is to soak the active substrate in a thiol solution; the soaking conditions include: a temperature of 20-25℃ and a time of 0.2-0.8h.

2. The application according to claim 1, wherein, The adhesion rate of the silver nanowires on the substrate is 70-80%; the adhesion rate of the gold nanospheres on the graphene layer is 50-70%.

3. The application according to claim 1, wherein, The silver nanowires are cylindrical with a diameter of 15-25 nm and a length of 25-35 μm. And / or, the content of the silver nanowires is 0.05-0.12 mg per square centimeter of substrate; And / or, the diameter of the gold nanospheres is 20-30 nm.

4. The application according to claim 1, wherein, The substrate is selected from glass substrate or semiconductor substrate.

5. The application according to claim 1, wherein, In step (1), the method of attaching silver nanowires, graphene layer and gold nanospheres to the substrate surface is to attach silver nanowires, graphene layer and gold nanospheres to the substrate surface in sequence.

6. The application according to claim 1, wherein, The silver nanowires were attached by first drop coating using a silver nanowire sol.

7. The application according to claim 1, wherein, The graphene layer is attached by using a graphene solution for a second drop coating.

8. The application according to claim 1, wherein, The gold nanospheres were attached by using a gold nanosphere sol for a third drop coating.

9. The application according to claim 6, wherein, The concentration of the silver nanowire sol is 0.5-3 mg / mL.

10. The application according to claim 6, wherein, The concentration of the silver nanowire sol is 1-2 mg / mL.

11. The application according to claim 6, wherein, The conditions for the first drop coating include: a temperature of 20-100℃; And / or, the amount of the silver nanowire sol may be 40-70 μL relative to the substrate per square centimeter.

12. The application according to claim 6, wherein, The conditions for the first drop coating include: a temperature of 30-80℃; And / or, the amount of the silver nanowire sol may be 50-60 μL relative to the substrate per square centimeter.

13. The application according to claim 7, wherein, The conditions for the second drop coating include: a temperature of 10-40℃; And / or, the concentration of the graphene solution is 0.01-0.8 mg / mL.

14. The application according to claim 7, wherein, The conditions for the second drop coating include a temperature of 15-30°C.

15. The application according to claim 7, wherein, The concentration of the graphene solution is 0.1-0.6 mg / mL.

16. The application according to claim 7, wherein, The amount of graphene solution used is 5-30 μL per square meter of glass substrate.

17. The application according to claim 7, wherein, The amount of graphene solution used is 10-20 μL per square meter of glass substrate.

18. The application according to claim 8, wherein, The concentration of the gold nanosphere sol is 0.1-2 mg / mL; And / or, the diameter of the gold nanospheres is 20-30 nm.

19. The application according to claim 8, wherein, The concentration of the gold nanosphere sol is 0.3-1 mg / mL.

20. The application according to claim 8, wherein, The conditions for the third drop application include: a temperature of 30-100℃; And / or, the amount of the gold nanosphere sol may be 10-30 μL relative to the substrate per square meter; And / or, the third drop is applied 1-4 times.

21. The application according to claim 8, wherein, The conditions for the third drop application include a temperature of 40-80℃.

22. The application according to claim 8, wherein, The amount of gold nanosphere sol used can be 15-25 μL per square meter of substrate.

23. The application according to claim 8, wherein, The third application is performed 2-3 times.

24. The application according to claim 1, wherein, The concentration of the thiol solution is 10. -4 -10 -1 mol / L.

25. The application according to claim 1, wherein, The concentration of the thiol solution is 10. -3 -10 -2 mol / L.

26. The application according to claim 1, wherein, The surface-enhanced Raman scattering composite substrate has a detection concentration of ≥10 pyrene. -6 mol / L.

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