阅读说明：本技术 基于多孔氮化镓的表面增强拉曼散射基底及其制备方法 (Surface enhanced Raman scattering substrate based on porous gallium nitride and preparation method thereof ) 是由 张宇 韩应宽 韩琳 于 2019-09-29 设计创作，主要内容包括：本发明公开了基于多孔氮化镓的表面增强拉曼散射基底及其制备方法,所述的基底包括多孔氮化镓基底和沉积在所述多孔氮化镓基底上的金/银复合表面,所述金/银复合表面内层为银层,外层为金层。该方法在多孔氮化镓基底上形成粗糙的金属表面,通过金属颗粒与下层多孔氮化镓的耦合达到拉曼增强的效应,解决现有技术成本高、设备复杂,增强效果不稳定,重复性差等问题。(The invention discloses a surface enhanced Raman scattering substrate based on porous gallium nitride and a preparation method thereof. According to the method, a rough metal surface is formed on the porous gallium nitride substrate, the Raman enhancement effect is achieved through the coupling of metal particles and the lower layer of porous gallium nitride, and the problems of high cost, complex equipment, unstable enhancement effect, poor repeatability and the like in the prior art are solved.)

1. The surface-enhanced Raman scattering substrate based on porous gallium nitride is characterized by comprising a porous gallium nitride substrate and a gold/silver composite surface deposited on the porous gallium nitride substrate, wherein the inner layer of the gold/silver composite surface is a silver layer, and the outer layer of the gold/silver composite surface is a gold layer.

2. The porous gallium nitride-based surface-enhanced raman scattering substrate according to claim 1, wherein the gallium nitride substrate is etched to have a uniform nanoporous structure by electrochemical etching.

3. The porous gallium nitride-based surface-enhanced raman scattering substrate of claim 1, wherein the silver layer is 10-50nm thick and the gold layer is 1-10nm thick.

4. The method for preparing a surface-enhanced Raman scattering substrate based on porous gallium nitride according to claim 1, comprising the steps of:

first, a 4-inch GaN substrate is selected with a doping concentration of 10¹⁸～10¹⁹cm^-1And cleaning, wherein the cleaning method comprises the following steps: ultrasonically cleaning with acetone for 5min, ultrasonically cleaning with anhydrous ethanol for 5min, ultrasonically cleaning with deionized water for 5min, and blow-drying with nitrogen gas;

secondly, forming conductive electrodes with different structures on the surface of the gallium nitride, and etching a uniform porous structure on the surface of the gallium nitride substrate by using an electrochemical etching method;

thirdly, taking the prepared large-area uniform porous gallium nitride as a template, and forming a gold/silver/porous gallium nitride composite structure on a porous gallium nitride substrate by an electron beam evaporation or sputtering method, wherein the specific method comprises the following steps: depositing silver of 10-50nm, and then depositing gold of 1-10nm to obtain a gold/silver/porous gallium nitride composite structure.

5. The method for preparing a surface-enhanced Raman scattering substrate based on porous gallium nitride according to claim 4, wherein in the second step, the adopted electrochemical etching equipment comprises a computer, a direct current power supply, an electrolyte and a platinum electrode, the electrolyte is oxalic acid, nitric acid or hydrochloric acid, and the concentration: 0.3 mol/L; the etching voltage is 10-20V, the etching time is 10-90min, the etched product is taken out and washed by deionized water, and the nitrogen is dried, so that the porous gallium nitride with the uniform nano-pore structure on the surface is prepared.

Technical Field

The invention belongs to the technical field of material analysis, and particularly relates to a surface enhanced Raman scattering substrate based on porous gallium nitride and a preparation method thereof.

Background

SERS has important applications in the fields of chemistry, material science, analytical science, surface science, biomedical research, and the like. SERS has unique advantages in bioanalysis over traditional bioanalytical methods: (1) the extremely low surface sensitivity of SERS is even lower to the single molecule level. (2) The SERS signal can reflect inherent molecular fingerprint information of a biological system; (3) compared with fluorescence, the SERS signal is stable and is suitable for long-term monitoring; (4) the peak of SERS is typically very narrow, 10-100 times narrower than the fluorescence emission of organic dyes or quantum dots; (5) SERS can realize multi-path detection under single-wavelength excitation; (6) filamentous nanostructures with different sizes, shapes, and coatings may be used for different detection purposes. Particularly, the substrate of the near-infrared laser light source is optimized, the natural autofluorescence phenomenon of a biological sample is avoided, and the light damage of visible light to living cells is reduced to the maximum extent. Thus, there has been a significant development in SERS and biomedical and chemical analysis applications thereof.

The generation of SERS signals requires a suitable substrate, and the key to the SERS effect is how to prepare metal surfaces with suitable nanostructures. Since the discovery of the SERS phenomenon, people are constantly developing and designing a preparation method of the SERS substrate, and with the development of technology, more and more methods emerge. The disordered surface is prepared by an initial electrochemical method, the nano particles with various sizes and shapes are synthesized, and the large-area surface nano structure is prepared by a template method. Methods for preparing efficient SERS substrates are numerous, including chemical etching, electrochemical etching, reactive ion etching, nanowire vapor growth, photolithography, and the like. However, these methods have problems of high cost, complicated equipment, unstable enhancement effect, poor repeatability and the like. At present, the biggest problem limiting the practical application of the technology is cost and stability.

Therefore, the design and development of the surface enhanced Raman scattering substrate with low cost, easy preparation, large area, high efficiency and high stability has great practical significance.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a surface enhanced Raman scattering substrate based on porous gallium nitride and a preparation method thereof, wherein the surface enhanced Raman scattering substrate has the advantages of low cost, large area, high sensitivity, good reproducibility and the like.

In order to solve the technical problems, the invention adopts the technical scheme that:

the surface enhanced Raman scattering substrate based on the porous gallium nitride comprises a porous gallium nitride substrate and a gold/silver composite surface deposited on the porous gallium nitride substrate, wherein the inner layer of the gold/silver composite surface is a silver layer, and the outer layer of the gold/silver composite surface is a gold layer.

Furthermore, the gallium nitride substrate is etched into a uniform nano-pore structure by an electrochemical etching method.

Furthermore, the thickness of the silver layer is 10-50nm, and the thickness of the gold layer is 1-10 nm.

The preparation method of the surface enhanced Raman scattering substrate based on the porous gallium nitride comprises the following steps:

first, a 4-inch GaN substrate is selected with a doping concentration of 10¹⁸～10¹⁹cm^-1And cleaning, wherein the cleaning method comprises the following steps: ultrasonically cleaning with acetone for 5min, ultrasonically cleaning with anhydrous ethanol for 5min, ultrasonically cleaning with deionized water for 5min, and blow-drying with nitrogen gas;

secondly, forming conductive electrodes with different structures on the surface of the gallium nitride, and etching a uniform porous structure on the surface of the gallium nitride substrate by using an electrochemical etching method;

thirdly, taking the prepared large-area uniform porous gallium nitride as a template, and forming a gold/silver/porous gallium nitride composite structure on a porous gallium nitride substrate by an electron beam evaporation or sputtering method, wherein the specific method comprises the following steps: depositing silver of 10-50nm, and then depositing gold of 1-10nm to obtain a gold/silver/porous gallium nitride composite structure.

Further, in the second step, the adopted electrochemical etching equipment comprises a computer, a direct current power supply, electrolyte and a platinum electrode, the electrolyte is oxalic acid or nitric acid or hydrochloric acid, and the concentration: 0.3 mol/L; the etching voltage is 10-20V, the etching time is 10-90min, the etched product is taken out and washed by deionized water, and the nitrogen is dried, so that the porous gallium nitride with the uniform nano-pore structure on the surface is prepared.

Compared with the prior art, the invention has the advantages that:

(1) the method aims at forming a rough metal surface on a porous gallium nitride substrate, achieving a Raman enhancement effect through coupling of metal particles and lower-layer porous gallium nitride, and solving the problems of high cost, complex equipment, unstable enhancement effect, poor repeatability and the like in the prior art; the method is simple and easy to operate, and can be used for preparing a large-area SERS substrate.

(2) The prepared SERS substrate surface hot spots are distributed uniformly and have large area and higher SERS signal repeatability.

(3) In addition, the substrate is of a gold/silver composite structure, and a layer of gold is covered on the surface of the silver, so that the enhancement effect is maintained, the oxidation of the silver is effectively prevented, and the stability of the enhancement effect of the substrate is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.

FIG. 1 is a schematic diagram of an electrochemical etching apparatus for preparing porous gallium nitride;

FIG. 2 shows the etched porous GaN structure substrate;

FIG. 3 shows a gold/silver/porous GaN structure substrate after metal deposition;

fig. 4 is a comparison of a reinforced substrate made according to the present invention with a conventional non-reinforced substrate.

Wherein, 1 is a computer, 2 is a direct current power supply, 3 is a sample, 4 is electrolyte, and 5 is a platinum electrode.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.

As shown in fig. 3, the surface-enhanced raman scattering substrate based on porous gallium nitride comprises a porous gallium nitride substrate and a gold/silver composite surface deposited on the porous gallium nitride substrate, wherein the inner layer of the gold/silver composite surface is a silver layer, the outer layer of the gold/silver composite surface is a gold layer, the thickness of the silver layer is 10-50nm, the thickness of the gold layer is 1-10nm, and the surface of the silver is covered with a layer of gold. The gallium nitride substrate is etched into a uniform nano-pore structure by an electrochemical etching method.

The preparation method of the surface enhanced Raman scattering substrate based on the porous gallium nitride is described as follows, which comprises the following steps:

first, a 4-inch GaN substrate is selected with a doping concentration of 10¹⁸～10¹⁹cm^-1And (6) cleaning. The cleaning method comprises the following steps: ultrasonically cleaning with acetone for 5min, ultrasonically cleaning with anhydrous ethanol for 5min, ultrasonically cleaning with deionized water for 5min, and blow-drying with nitrogen for use.

And secondly, forming conductive electrodes with different structures on the surface of the gallium nitride, and etching a uniform porous structure on the surface of the gallium nitride substrate by using an electrochemical etching method. Shown in fig. 1 of the used electrochemical etching equipment, the electrochemical etching equipment comprises a computer 1, a direct-current power supply 2, an electrolyte 4, a platinum electrode 5 and a sample 3, wherein the used electrolyte can be oxalic acid, nitric acid or hydrochloric acid, and the embodiment selects oxalic acid and has the concentration: 0.3 mol/L; the etching voltage is 10-20V, the etching time is 10-90min, the substrate is taken out after etching and washed by deionized water, and nitrogen is blown dry to prepare the porous gallium nitride with the uniform surface and the nano-pore structure, as shown in figure 2.

The step forms a conductive electrode on the surface of the gallium nitride, and the uniformity of etching current in the etching process is improved, so that the uniformity of etched porous gallium nitride is improved. The etching device adopts a two-electrode mode, simplifies the preparation device and reduces the cost.

And thirdly, forming a gold/silver/porous gallium nitride composite structure on the porous gallium nitride substrate by using the prepared large-area uniform porous gallium nitride as a template through an electron beam evaporation or sputtering method. The specific method comprises the following steps: depositing silver of 10-50nm, and then depositing gold of 1-10nm to obtain a gold/silver/porous gallium nitride composite structure shown in figure 3.

To verify the effectiveness of the surface enhanced raman scattering substrate of the present invention, it was examined and compared to a substrate without raman enhancement.

Firstly, a solution of rhodamine 6G is prepared, and the concentration of the rhodamine 6G (R6G) is 1 multiplied by 10^-6M。

And (3) preparing one gold/silver/porous gallium nitride surface enhanced Raman scattering substrate according to the embodiment, taking one porous gallium nitride substrate, respectively dropwise adding 2ul of the prepared rhodamine 6G solution, airing, and respectively placing the substrate under a Raman instrument to measure the Raman spectrum of R6G. Referring to fig. 4, it is evident that the substrate of the present invention significantly improves the characteristic peak of the detector molecule R6G.

In order to verify the uniformity of the surface enhanced raman scattering substrate of the present invention, SERS mapping was tested to characterize its uniformity.

Firstly, a solution of rhodamine 6G is prepared, and the concentration of the rhodamine 6G (R6G) is 1 multiplied by 10^-6M。

The gold/silver/porous gallium nitride surface enhanced Raman scattering substrate prepared according to the embodiment is respectively dripped with 2ul of the prepared rhodamine 6G solution, the substrate is respectively placed under a Raman instrument after being dried to measure mapping spectrum of R6G, and experiments prove that the substrate has better uniformity.

In conclusion, the method is simple and easy to operate, the large-area SERS substrate can be prepared, and the prepared SERS substrate has the advantages of uniform distribution of hot spots on the surface, large area and higher repeatability of SERS signals.

It is understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art should understand that they can make various changes, modifications, additions and substitutions within the spirit and scope of the present invention.