CN205691505U - Nanometer annular chamber SERS substrate based on surface phasmon effect - Google Patents

Abstract

The utility model discloses a nano ring cavity SERS substrate based on the surface plasmon effect, which comprises a substrate, on which a nanoscale single-layer PS microsphere array is arranged, and the PS microsphere array is filled with SiO ₂ or TiO ₂ The gel layer formed by the precursor solution, the thickness of the gel layer is smaller than the diameter of the microsphere, and there is a nanoscale annular cavity between the top of the PS microsphere and the gel layer, and the surface layer of the substrate is also covered with a metal layer, covered with The annular cavities of the metal layer form an array of metallic annular cavities. The sample to be detected is filled in the annular concave cavity, and cylindrical surface plasmons are formed in the metal annular cavity when the light is illuminated, forming a strong local electric field enhancement, and the sample to be detected excites a detectable Raman signal with the help of the enhanced electric field , simple in structure and easy to process and prepare.

Description

Nano ring cavity SERS substrate based on surface plasmon effect

technical field

The utility model relates to a nano ring cavity SERS substrate based on the surface plasmon effect, and belongs to the technical field of element spectrum analysis of the surface plasmon effect.

Background technique

In general, it is very convenient to use Raman spectroscopy to identify the composition of substances, but for many chemical substances, the signal cannot be detected directly through Raman spectroscopy. It is necessary to use Raman enhancement technology to improve the signal-to-noise ratio of Raman signals to detect substance to be tested. The surface-enhanced Raman scattering (SERS) effect refers to that in some specially prepared metal good conductor surfaces or sols, in the excitation region, due to the enhancement of the electromagnetic field on the surface or near the surface of the sample, the Raman scattering signal of the adsorbed molecules is larger than that of the ordinary Raman scattering signal. Mann scattering (NRS) signal greatly enhanced phenomenon.

Surface-enhanced Raman overcomes the shortcomings of low sensitivity of Raman spectroscopy, and can obtain structural information that is not easily obtained by conventional Raman spectroscopy. It is widely used in surface research, surface state research on adsorption interfaces, interface orientation and configuration of biological molecules, Conformation research, structural analysis, etc., can effectively analyze the adsorption orientation of compounds on the interface, the change of adsorption state, and interface information. Making a substrate that can enhance the Raman signal to a greater extent has always been the goal that people are striving for.

At present, the SERS mechanisms generally accepted by the academic circle mainly include physical enhancement mechanism and chemical enhancement mechanism.

One is the electromagnetic field enhancement (Electromagnetic enhancement, EM) mechanism: the local electromagnetic field enhancement caused by the surface plasmon resonance (Surface plasmon resonance, SPR) is considered to be the most important contribution. Under the collective oscillation effect. Since the energy gaps of d electrons and s electrons of Cu, Ag, and Au are larger than those of transition metals, the group IB metals are less prone to interband transitions. As long as the appropriate excitation light wavelength is selected for these three metal systems, the energy of absorbed light can be avoided from being converted into heat due to the occurrence of interband transitions, thus tending to realize the efficient SPR scattering process.

The other is the chemical interaction, which is mainly manifested in the difficulty of electron density deformation under the photoelectric field in the Raman process. When molecules are chemisorbed on the surface of the substrate, the surface, surface adatoms and other co-adsorbed species may have certain chemical interactions with the molecules. Variation affects its Raman strength.

In the prior art, the SERS signal is often enhanced by increasing the local electric field intensity through the surface plasmon effect. The surface plasmon is a special electromagnetic wave mode existing at the interface between metal and medium. It is the surface charge density wave and The coupling of the electromagnetic wave excited by it is a kind of transverse wave. Surface plasmons have a strong local electric field strength, and the SERS signal can be effectively enhanced by exciting surface plasmons. At present, the commonly used SERS is silver sol or silver nanoparticles. This method is suitable for the visible band. The enhancement effect of silver particles is not very high, and it is granular, which cannot meet all applications.

In recent years, a variety of nano-metal periodic structures have been used as SERS substrates. The array of annular slits open at both ends has a good enhancement effect, but it is difficult to process and is generally suitable for laboratory research and difficult to scale production.

Utility model content

The purpose of the utility model is to overcome the deficiencies in the prior art, provide a nano-annular cavity SERS substrate based on the surface plasmon effect and its manufacturing method, and solve the problem of complex structure of the SERS substrate in the prior art that leads to processing difficulties technical problem.

In order to solve the above technical problems, the utility model provides a nano-annular cavity SERS substrate based on the surface plasmon effect, including a substrate, which is characterized in that a nanoscale single-layer PS microsphere array is arranged on the substrate, and the PS microspheres The ball array is filled with a gel layer formed by SiO ₂ or TiO ₂ precursor solution. The thickness of the gel layer is smaller than the diameter of the microspheres. There is a nanoscale annular cavity between the top of the PS microspheres and the gel layer. On the substrate The surface layer of the metal layer is also covered with a metal layer, and the annular cavity covered with the metal layer forms a metal annular cavity array.

Further, the diameter of the PS microsphere ranges from 200nm to 700nm, and the deviation rate of the diameter of the PS microsphere is less than 0.2%.

Further, the SiO ₂ precursor solution is a mixture of TEOS (98wt%), 0.1M/L HCl and absolute ethanol, and the TiO ₂ precursor solution is TiBALDH (10wt%).

Further, the thickness of the gel layer is in the range of 0.3-0.9 times the diameter of the PS microspheres.

Further, the cross-section of the top of the PS microsphere is an Ω arc, and there is a bend at the edge of the arc near the gel layer.

Further, the diameter of the annular cavity is less than 1 micron, and the slit width of the cavity is less than 250 nanometers.

Further, the thickness of the metal layer is 20nm-600nm, and the metal layer is gold, silver or copper.

Compared with the prior art, the beneficial effects achieved by the utility model are:

1) The surface of the SERS substrate of the present invention has a metal annular cavity array, and the sample to be tested is filled in the annular cavity. When the light is illuminated, a cylindrical surface plasmon will be formed in the metal annular cavity, forming a strong local electric field enhancement. , the detection sample filled in the cavity excites a detectable Raman signal with the help of an enhanced electric field; and this cavity can realize cylindrical surface plasmons without periodicity; the utility model has a simple structure and is suitable for processing and production ;

2) The method of the utility model uses nano-microspheres and sol-gel to prepare a disordered array of annular cavities on a flat substrate. The prepared microspheres are closely combined with the substrate, have good mechanical properties, and are not easy to fall off. At the same time, the density and size of the annular cavity are controllable , several sizes of nano ring cavities can be fabricated on the same substrate using the same process; it is suitable for different excitation wavelengths, has good repeatability, and achieves good detection results; the material of the nano ring cavity can also be flexibly selected from gold, Silver, copper etc., the applicability of the utility model is strong.

Description of drawings

Fig. 1 is a structural schematic diagram of the utility model SERS substrate;

Fig. 2 is the schematic flow chart of the manufacturing method of SERS substrate of the present invention;

Fig. 3 is a Raman spectrum using a SERS substrate in Embodiment 1 of the present invention.

Reference signs: 1. substrate; 2. PS microsphere; 3. gel layer; 4. annular cavity; 5. metal layer; 6. microscope objective lens.

detailed description

Below in conjunction with accompanying drawing, the utility model is further described. The following examples are only used to illustrate the technical solution of the utility model more clearly, but not to limit the protection scope of the utility model.

As shown in Figure 1, a nano-annular cavity SERS substrate based on the surface plasmon effect of the present invention includes a substrate 1, which is characterized in that the substrate 1 is provided with nano-scale polystyrene (PS) Microsphere array, the PS microsphere 2 array is covered with a gel layer 3 with a thickness smaller than the PS microsphere diameter, and a nanoscale annular cavity 4 is provided between the top of the PS microsphere 2 and the gel layer 3, and the annular cavity 4 The surface layer of the substrate 1 is also covered with a metal layer 5, forming a metal annular cavity array on the surface of the substrate 1.

The cross-section of the metal annular cavity is shown at B in Figure 1. The PS microspheres are partially submerged in the gel layer. The cross-section of the top of the PS microspheres is Ω arc-shaped, and there is a fold at the edge of the arc near the gel layer. Bend, and the gel layer just forms an annular cavity, and the surface of the annular cavity is also covered with a metal layer. The array of annular cavities is shown in the top view at A in Figure 1, and the array of annular cavities can be disordered. When the SERS substrate is used, the enhancement principle is that the sample to be detected is filled in the annular cavity, and cylindrical surface plasmons will be formed in the metal annular cavity when the light is illuminated, forming a strong local electric field enhancement, and the cavity enhances the electric field. The local effect also limits the exit direction of the Raman signal and makes it easy to detect the signal, so it is called a cavity instead of a slit. The detection sample filled in the cavity excites a detectable Raman signal with the help of an enhanced electric field. The excitation light is focused to the sample surface through the microscope objective lens 6, and the Raman light is also returned from the sample surface through the microscope objective lens 6, thereby realizing the Raman signal. detection. It can also be detected by macroscopic Raman. At this time, there is no need for a microscope objective lens. The role of the objective lens is to realize the detection of microscopic regions; and this kind of cavity does not need to be periodic: light can be constrained by waveguides and upper and lower interfaces in a single ring cavity to form surfaces, etc. The ion polariton effect does not need periodic momentum matching, and the function of the array is to enhance the SERS signal intensity, which is easy to detect.

Further, the PS microsphere particle size ranges from 200nm to 700nm, and the PS microsphere diameter deviation/average diameter×100%<0.2%.

Further, the SiO precursor solution is a mixture of TEOS (98wt%), 0.1M/L HCl and absolute ethanol, and the _TiO precursor solution is _TiBALDH (10wt%); utilize the precursor solution to make PS microspheres and The substrate is closely combined, has good mechanical properties, and is not easy to fall off.

Further, the diameter of the annular cavity is less than 1 micron, and the slit width of the cavity is less than 250 nanometers. The size of the annular cavity on the same substrate can be uniform, or several types of cavities with fixed sizes can be randomly distributed. The density and size of the cavity can be flexibly and conveniently selected according to different excitation wavelengths to match the excitation wavelength and achieve good detection results.

Furthermore, the thickness of the metal layer is 20nm-600nm, and the metal layer is usually a noble metal film, which can be gold, silver or copper, which has many options and strong applicability.

Correspondingly, the manufacturing method of the SERS substrate of the present invention comprises the following steps:

S1, take a round flat substrate, after it is cleaned and dried, place it on the tray of the glue homogenizer;

The specific process of substrate treatment is as follows: first, ultrasonic cleaning with acetone, alcohol, and deionized water, soaking in 80-degree concentrated sulfuric acid, then rinsing with distilled water, and finally blowing dry with nitrogen;

S2, configuring SiO ₂ or TiO ₂ precursor solution;

The mass ratio of the precursor solution of SiO2 is—tetraethyl orthosilicate TEOS (98wt%): the HCl of 0.1M/L: dehydrated alcohol=1:1:1.5, the aqueous solution of the precursor of TiO2 TiBALDH (10wt%);

S3, a colloidal microsphere solution mixed with nano-scale microspheres of polystyrene (PS) material and deionized water, the volume ratio is 1:1000 to 1:50;

The particle size range of microspheres is 200nm to 700nm, PS microsphere diameter deviation/average diameter×100%<0.2%;

S4, after mixing the precursor solution and the colloidal microsphere solution, drop it on the substrate, start the glue homogenizer, and evenly spin-coat the PS microsphere array on the surface of the substrate;

The mixing volume ratio is about 1:5000, the precursor solution acts as a glue, and the PS microspheres are initially glued to the substrate. The PS microsphere array using the sol-gel spin coating method of the homogenizer can be disordered. ;

S5, dilute the precursor solution and add it dropwise to the PS microsphere layer, start the gel homogenizer, and evenly spin-coat a layer of gel layer with a thickness smaller than the diameter of the microsphere on the PS microsphere array;

After dilution, the thickness of each spin coating can be reduced, which is convenient for controlling the thickness of the gel layer. Repeat step 5 according to the structure size required by the test to adjust the thickness of the gel layer; the thickness of the gel layer is generally in the range of 0.3-0.9 times the microsphere diameter;

S6, performing reactive ion etching on the top of the PS microsphere exposing the gel layer, forming a nanoscale annular cavity between the top of the PS microsphere and the gel layer;

The size of the annular cavity can be adjusted according to the needs of the experiment. The depth of etching on the top of the PS microsphere can also be adjusted by adjusting the thickness of the gel layer.

S7, sputtering a layer of metal film on the surface of the entire substrate to form a SERS substrate with a metal nano ring cavity array on the surface.

A layer of metal film is sputtered by a magnetron sputtering coating machine, and the metal film can be a gold, silver or copper film with a thickness ranging from 20nm to 600nm.

Embodiment one

The steps of preparing the annular cavity SERS substrate are described in detail in conjunction with specific embodiments as follows:

a) Take a 2.5-inch silicon wafer, wash it with acetone (purity 99.7%), alcohol (purity 99.9%), deionized water (resistivity 18.2MΩ) ultrasonic (40W) for 10 minutes, and then use nitrogen gas (purity 99.7%) Blow dry; then process the silicon wafer with a plasma cleaner for 5 minutes;

b) Place the treated silicon wafer substrate on the tray of the homogenizer, and set the speed at 3000 rpm;

c) configure the precursor solution of SiO ₂ , the mass of each substance in the precursor solution of SiO ₂ is: TEOS (98wt%)=1g, 0.1M/L HCl=1g, EtOH (100%)=1.5g, mix Stir for one hour and set aside;

d) 20ml of colloidal microsphere solution configured with polystyrene (PS) microspheres, wherein the diameter of PS microspheres is 690nm, the diameter deviation rate is 0.2%, the volume percentage concentration is 0.05%, and the solvent is deionized water;

e) Add the precursor solution configured in c) to the colloidal microsphere solution configured in d) to form a solution, and the added volume percentage is 0.5%, that is, 0.01ml;

f) Add the solution configured in step e) dropwise to the silicon chip substrate in b), start the glue homogenizer, and evenly spin-coat one layer of PS microspheres on the plane, as shown in Figure 2;

g) Dilute the TEOS solution configured in step c) by 10 times and drop it on the flat substrate in f), and set the spin coating at a speed of 3000 rpm, as shown in Figure 2;

h) and repeat step g) 2 times according to the designed structural size, and coat a composite film of polystyrene microspheres and silica gel on the surface of the plane substrate, the thickness of the gel is about 300nm;

i) Reactive ion etching is used to partially remove the PS microspheres from the thin film obtained in step h), and then a 200nm thick metal silver film is sputtered by a magnetron sputtering coating machine to form a metal nano ring cavity array SERS substrate, as shown in Figure 1.

h) Adenine detection on the above SERS substrate. Soak the substrate made in the above example in adenine solutions of different concentrations (1E-8M/L, 1E-7M/L, 1E-6M/L, 1E-5M/L, 1E-4M/L) for 1h, take out Rinse and blow dry, use 514nm laser, 20mW, integration time 45s. The reference is the Raman spectrum of the silver film on the silicon wafer under the same conditions, and the measurement results are shown in Figure 3, and the peak of the Raman signal is detected.

The above is only a preferred embodiment of the utility model, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the utility model, some improvements and modifications can also be made. And modification should also be regarded as the protection scope of the present utility model.

Claims (6)

1. A nano-annular cavity SERS substrate based on the surface plasmon effect, including a substrate, characterized in that the substrate is provided with a nanoscale single-layer PS microsphere array, and the PS microsphere array is filled with SiO2 or TiO2 precursor The gel layer formed by the substance solution, the thickness of the gel layer is less than the diameter of the microsphere, there is a nano-scale annular cavity between the top of the PS microsphere and the gel layer, and the surface layer of the substrate is also covered with a metal layer, covered with a metal layer. The annular cavities of the layers form an array of metallic annular cavities. 2. A nano-annular cavity SERS substrate based on the surface plasmon effect according to claim 1, characterized in that, the PS microsphere diameter ranges from 200 nm to 700 nm, and the PS microsphere diameter deviation rate is less than 0.2% . 3. A nano-annular cavity SERS substrate based on the surface plasmon effect according to claim 1, wherein the thickness of the gel layer is in the range of 0.3-0.9 times the diameter of the PS microsphere. 4. A kind of nano-annular cavity SERS substrate based on surface plasmon effect according to claim 1, it is characterized in that, the cross section of PS microsphere top is Ω arc, near the arc edge of gel layer There are bends. 5. A nano-annular cavity SERS substrate based on the surface plasmon effect according to claim 1, characterized in that the diameter of the annular cavity is less than 1 micron, and the slit width of the cavity is less than 250 nm. 6 . A nano-annular cavity SERS substrate based on surface plasmon effect according to claim 1 , wherein the thickness of the metal layer is 20nm-600nm, and the metal layer is gold, silver or copper.