阅读说明：本技术 一种表面增强拉曼散射基底及其制备方法 (Surface-enhanced Raman scattering substrate and preparation method thereof ) 是由 周宇 托尼·卡斯 丹尼尔·埃尔森 徐建华 周玄 杨光 于 2020-11-09 设计创作，主要内容包括：本发明公开一种表面增强拉曼散射基底及其制备方法,首先,在玻璃盖玻片上沉积SU-8膜,涂布后,采用UV照射30分钟；然后将其浸泡于乙醇胺与磷酸钠缓冲液形成的混合液中,并进行温和搅拌；指定时长后,进行洗涤,并浸入3-氨基丙基三乙氧基硅烷的2-丙醇溶液中,浸泡一定时间后,进行洗涤,然后浸泡至金纳米颗粒溶液中指定时长后再次进行洗涤。(The invention discloses a surface-enhanced Raman scattering substrate and a preparation method thereof, and the surface-enhanced Raman scattering substrate is prepared by the steps of firstly, depositing an SU-8 film on a glass cover glass, and irradiating for 30 minutes by adopting UV after coating; then soaking the mixture in a mixed solution formed by ethanolamine and sodium phosphate buffer solution, and carrying out mild stirring; and after a specified time, washing, soaking in a 2-propanol solution of 3-aminopropyltriethoxysilane, washing after soaking for a certain time, and then washing again after soaking in a gold nanoparticle solution for a specified time.)

1. The surface-enhanced Raman scattering substrate is characterized by comprising a glass cover glass, a modified SU-8 film covering the glass cover glass, and a gold nanoparticle layer adsorbed on the modified SU-8 film.

2. A method of preparing a surface-enhanced raman scattering substrate according to claim 1, comprising the steps of:

depositing an SU-8 film on a glass cover glass, and irradiating for 30 minutes by adopting UV after coating;

soaking the glass cover glass covered with the SU-8 film in a mixed solution formed by ethanolamine and a sodium phosphate buffer solution, and stirring at a speed of not higher than 600rpm for a specified time;

taking out the glass cover glass, washing, and immersing into a 2-propanol solution of 3-aminopropyltriethoxysilane in a specified volume ratio;

after soaking for a specified time, taking out the glass cover glass, and washing to form a modified SU-8 film;

soaking the glass cover glass covered with the modified SU-8 film in the gold nanoparticle solution for a specified time, and adsorbing the gold nanoparticles onto the modified SU-8 film; and

the glass cover slips were washed.

3. The method of claim 2, wherein a 40 μm SU-8 film is deposited on a circular glass cover glass 22mm in diameter using a spray coater at 3000rpm to form the SU-8 film.

4. The method according to claim 2, wherein the ethanolamine concentration is 0.1Mol/L, the sodium phosphate buffer concentration is 0.5Mol/L, and the pH of the mixture of ethanolamine and sodium phosphate buffer is 7.4.

5. The method according to claim 3, wherein the glass coverslip covered with SU-8 thin film is soaked in a mixture of ethanolamine and sodium phosphate buffer for 10 hours.

6. The method of claim 2, wherein the glass coverslip removed from the mixture of ethanolamine and sodium phosphate buffer is washed with 2-propanol.

7. The method of claim 2, wherein the 3-aminopropyltriethoxysilane is present in a 2-propanol solution at a volume ratio of 2%.

8. The method of claim 7, wherein the cover glass is soaked in a solution of 3-aminopropyltriethoxysilane in 2-propanol for 90 minutes.

9. The method of claim 2, wherein the glass cover slip is soaked in the gold nanoparticle solution for 2 hours.

10. The method of claim 2, wherein the glass coverslip removed from the 2-propanol solution of 3-aminopropyltriethoxysilane and the glass coverslip removed from the gold nanoparticle solution are washed with ultrapure water and absolute ethanol.

Technical Field

The invention relates to the field of nanotechnology, in particular to a surface enhanced Raman scattering substrate and a preparation method thereof.

Background

Surface enhanced raman scattering SERS has been widely used to detect food additives, drugs, pesticides and some contaminants with detection limits down to single molecule levels, with high sensitivity and excellent molecular specificity. The key to successful detection using SERS is the formation of a high gap density of less than 10nm, which can also be referred to as a hot spot. When the detection object is attached to these hot spots, the raman scattering signal will be greatly enhanced.

From an application point of view, developing an effective SERS substrate needs to provide a high gap density with a strong enhancement factor, and maintain high stability and reproducibility. The preparation method of the SERS substrate commonly used at present comprises a patterning technology, a self-assembly technology and the like, wherein the patterning technology such as electron beam lithography, nanosphere lithography or nanoimprint can improve the reproducibility of the SERS substrate, but high-density hot spots are difficult to generate under a certain molecular concentration, and especially the gap size is less than 20 nm. While the self-assembly technique can introduce symmetry to control the gap size within a certain range, the preparation process is very complicated and time-consuming, and is very difficult to manufacture over large areas.

Therefore, it is challenging and necessary to develop a simple, fast and reproducible method for preparing a surface-enhanced raman scattering active substrate.

Disclosure of Invention

Aiming at partial or all problems in the prior art, the invention provides a surface-enhanced Raman scattering substrate on one hand, which comprises a glass cover glass, a modified SU-8 film covered on the glass cover glass, and a gold nanoparticle layer adsorbed on the modified SU-8 film.

In another aspect, the present invention provides a method for preparing the surface-enhanced raman scattering substrate, including:

preparing an SU-8 thin film, depositing the SU-8 thin film on a glass cover glass, and irradiating by adopting UV after coating;

forming a modified SU-8 film comprising:

soaking the glass cover glass covered with the SU-8 film in a mixed solution formed by ethanolamine and a sodium phosphate buffer solution, and stirring at a speed of not higher than 600rpm for a specified time;

taking out the glass cover glass, washing, and immersing into a 2-propanol solution of 3-aminopropyltriethoxysilane in a specified volume ratio; and

after soaking for a specified time, taking out the glass cover glass, and washing to form a modified SU-8 film;

soaking the glass cover glass covered with the modified SU-8 film in the gold nanoparticle solution for a specified time, and adsorbing the gold nanoparticles onto the modified SU-8 film; and

the glass cover slips were washed.

Further, the deposition of the SU-8 film was done by a spray coater.

Further, the sprayer deposits a 40 μm SU-8 film on a circular glass cover glass 22mm in diameter at 3000 rpm.

Further, the concentration of the ethanolamine is 0.1Mol/L, the concentration of the sodium phosphate buffer solution is 0.5Mol/L, and the pH value of a mixed solution formed by the ethanolamine and the sodium phosphate buffer solution is 7.4.

Further, the glass cover slip covered with the SU-8 film is soaked in a mixed solution of ethanolamine and sodium phosphate buffer for 10 hours.

Further, the glass cover glass taken out from the mixture of ethanolamine and sodium phosphate buffer was washed with 2-propanol.

Further, the volume ratio of the 2-propanol solution of the 3-aminopropyltriethoxysilane was 2%.

Further, the cover glass was soaked in a solution of 3-aminopropyltriethoxysilane in 2-propanol for 90 minutes.

Further, the glass cover glass taken out from the 2-propanol solution of 3-aminopropyltriethoxysilane was washed with ultrapure water and anhydrous ethanol.

Further, the glass cover plate was soaked in the gold nanoparticle solution for 2 hours.

Further, the gold nanoparticle solution is a gold nanorod or gold nanostar solution.

Further, the glass cover glass taken out of the gold nanoparticle solution was washed with ultrapure water and anhydrous ethanol.

In the present invention, the SU-8 film refers to a commonly used epoxy-based negative photoresist, and negative refers to a photoresist, which is capable of crosslinking the portion exposed to ultraviolet rays, while the rest of the film remains soluble and can be washed away during development, and the molecular structure of the SU-8 is shown in fig. 6.

According to the surface-enhanced Raman scattering substrate and the preparation method thereof, the gold nanorods and/or the gold nanostars are attached to the surface of the SU-8 thin film by a chemical method to prepare the surface-enhanced Raman scattering active substrate, and the surface-enhanced Raman scattering active substrate has excellent realizable reproducibility and high enhancement factors. Meanwhile, the SU-8 is modified by a simple chemical method, so that the gold nanoparticles are firmly adsorbed on the surface of the modified SU-8 film through electrostatic adsorption, and the preparation is simple and quick. And the utilization of the gold nanorods and the gold nanostars enables the substrate to generate a large number of hot spots, thereby greatly enhancing the Raman scattering signal of the detection object. Meanwhile, the random adsorption of the analyte is greatly avoided or reduced by using a large amount of nano particles, and the reproducibility is greatly improved.

Drawings

To further clarify the above and other advantages and features of embodiments of the present invention, a more particular description of embodiments of the present invention will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings, the same or corresponding parts will be denoted by the same or similar reference numerals for clarity.

Fig. 1 is a schematic flow chart of a method for preparing a surface-enhanced raman scattering substrate according to an embodiment of the present invention;

FIG. 2 shows a schematic diagram of gold nanoparticle adsorption after SU-8 membrane modification;

FIG. 3 shows a schematic view of the adsorption of gold nanostar particles;

FIG. 4a is an SEM image of a gold nanorod substrate obtained by a method for preparing a surface enhanced Raman scattering substrate according to an embodiment of the invention;

fig. 4b shows an SEM image of a gold nanostar substrate obtained by a method for preparing a surface enhanced raman scattering substrate according to an embodiment of the present invention;

fig. 5 shows raman scattering spectra of rhodamine 6G on a blank SU-8 substrate, a gold nanorod substrate and a gold nanostar substrate obtained by the method for preparing a surface enhanced raman scattering substrate according to an embodiment of the present invention; and

FIG. 6 shows a schematic of the molecular structure of SU-8 membrane.

Detailed Description

In the following description, the present invention is described with reference to examples. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other alternative and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. Similarly, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the embodiments of the invention. However, the invention is not limited to these specific details. Further, it should be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

Reference in the specification to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

It should be noted that the embodiment of the present invention describes the process steps in a specific order, however, this is only for the purpose of illustrating the specific embodiment, and does not limit the sequence of the steps. Rather, in various embodiments of the present invention, the order of the steps may be adjusted according to process adjustments.

The invention provides a simple, rapid and reproducible surface-enhanced Raman scattering active substrate and a preparation method thereof. The surface-enhanced Raman scattering substrate comprises a glass cover glass, a modified SU-8 film covering the glass cover glass, and a gold nanoparticle layer adsorbed on the modified SU-8 film.

The flow of the preparation method of the surface-enhanced raman scattering substrate is shown in fig. 1, and comprises the following steps:

first, in step 101, an SU-8 film is prepared. If a glass substrate is simply adopted, the nano-particle adsorption is not strong and unstable, and the nano-particle is very easy to fall off, so that in order to enhance the stability of nano-particle adsorption, the surface enhanced Raman scattering substrate is prepared on the basis of an SU-8 film, and the preparation of the SU-8 film comprises the following steps: depositing an SU-8 film on a glass cover glass, and after coating, performing UV irradiation to crosslink the SU-8 film; in one embodiment of the invention, a 40 μm SU-8 film was deposited on a circular glass cover slip 22mm in diameter using a spray coater at 3000rpm to form a SU-8 thin film, and in yet another embodiment of the invention, UV irradiation was performed for 30 minutes after coating;

next, at step 102, a modified SU-8 film is formed. In order to enable gold nanoparticles to be adsorbed on the surface of a substrate through electrostatic adsorption, the SU-8 film needs to be modified, and fig. 2 and 3 show adsorption schematic diagrams of the modified gold nanoparticles, so that layer gold nanostar particles are uniformly distributed on the surface of the gold nanoparticles, the gold nanostar particles are distributed uniformly, the star-shaped morphology features of the gold nanostar particles are clear and recognizable, and the modified SU-8 film is formed by the following steps:

firstly, soaking a glass cover glass covered with an SU-8 film in a mixed solution formed by ethanolamine and a sodium phosphate buffer solution, and carrying out mild stirring for a specified time; in one embodiment of the invention, the concentration of the ethanolamine is 0.1Mol/L, the concentration of the sodium phosphate buffer solution is 0.5Mol/L, and the pH value of a mixed solution formed by the ethanolamine and the sodium phosphate buffer solution is 7.4; in another embodiment of the invention, the glass cover slip covered with the SU-8 film is soaked in a mixed solution of ethanolamine and sodium phosphate buffer for 10 hours; wherein the mild stirring is not higher than 600 rpm;

next, the glass cover glass is taken out, washed and immersed into a 2-propanol solution of 3-aminopropyltriethoxysilane at a specified volume ratio; in one embodiment of the invention, the glass cover glass taken out of the mixed solution of ethanolamine and sodium phosphate buffer is washed by 2-propanol, and in another embodiment of the invention, the volume ratio of the 3-aminopropyltriethoxysilane in 2-propanol is 2%; and

finally, after soaking for a specified time, taking out the glass cover glass, and washing to form a modified SU-8 film; the surface of the modified SU-8 membrane is positively charged and can adsorb gold nanoparticles; in one embodiment of the invention, the specified time period is 90 minutes; in yet another embodiment of the present invention, glass coverslips removed from a 2-propanol solution of 3-aminopropyltriethoxysilane are washed with ultrapure water and absolute ethanol;

next, at step 103, gold nanoparticles are adsorbed. Soaking the glass cover glass covered with the modified SU-8 film in the gold nanoparticle solution for a specified time, and adsorbing the gold nanoparticles onto the modified SU-8 film; in one embodiment of the invention, the specified duration is 2 hours; in yet another embodiment of the present invention, the gold nanoparticle solution is a gold nanorod or gold nanostar solution; and

finally, at step 104, washing. And washing the glass cover glass, and washing off suspended and incompletely adsorbed gold nanoparticles to obtain a stable substrate. In one embodiment of the present invention, the glass cover glass taken out from the gold nanoparticle solution is washed with ultrapure water and absolute ethanol.

In order to verify the effect of the preparation method of the surface-enhanced raman scattering substrate in the embodiment of the invention, the gold nanorod substrate and the gold nanostar substrate prepared by the method are detected:

first, SEM images were taken to evaluate the immobilization effect of gold nanoparticles on the SU-8 thin film, and SEM images of the gold nanorod substrate and the gold nanostar substrate are shown in fig. 4a and 4 b. In fig. 4a, gold nanorods are distributed on the surface of a variably modified SU-8 film and show a clear shape and size. Due to the solvent evaporation effect, the spacing between the formed nanoparticle patterns is between 25 and 500 nm. In fig. 4b, gold nanostar aggregates adhered to the modified SU-8 film, no star tips were observed due to the need to spray a 5nm chromium coating covering the star tips to form a sphere when taking SEM images; and

then, the prepared gold nanorod substrate and the prepared gold nanostar substrate are respectively treated at the concentration of 10^-4Soaking in Mol/L ethanol solution of rhodamine 6G (R6G). After 10 minutes, the substrate was washed with water and ethanol and dried at room temperature, and then all Raman and SERS spectra were recorded using an InVia Renishaw Raman spectrometer and a 633nm HeNe laser exposed for 10s under a 50-fold objective lens. The laser power was set to 0.5 mW. For comparison, while measurements were performed on a blank SU-8 substrate in the same setup, the raman scattering spectra of each substrate are shown in fig. 5, and the raman scattering spectra on a blank substrate without gold nanoparticles are shown in the bottom most curve of fig. 5, with no characteristic raman peak observed. In FIG. 5, the Raman scattering spectrum of the gold nanorod substrate in the middle and the Raman scattering spectrum of the gold nanostar substrate at the top are shown, and it can be seen that there appears a distinct peak that is completely consistent with the Raman spectrum of the standard R6G, wherein 612cm^-1The peak at (A) is due to the in-plane vibration of the C-C deformation, and 772cm^-1The peak at (a) is related to the out-of-plane curvature of the C-H deformation, 1184cm^-1The peak at (B) then corresponds to the C-C tensile vibration, and 1312cm^-1、1362cm^-1、1511cm^-1、1573cm^-1And 1650cm^-1The peak at (a) is due to aromatic C-C tensile vibrations. Then 1511cm^-1As a standard, the SERS Enhancement Factor (EF) of the gold nanoparticles was calculated using the following formula:

wherein, I_SERSAnd I_RSRespectively represents the Raman signal intensity of the same peak in the SERS spectrum on the gold nanoparticle substrate and the initial Raman spectrum of the blank substrate. N is a radical of_SERSAnd N_RSIndicating the number of R6G molecules attached to the substrate in the area of the laser spot. Through calculation, the SERS enhancement factor of the gold nanorod substrate is 2.5 multiplied by 10⁴The SERS enhancement factor of the golden nano star substrate is 4.6 multiplied by 10⁵. The SERS enhancement factor of gold nanostars is higher due to the hot spots of the tips and the hot spots between particles.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.