CN-122016752-A - Preparation method and application of LSPR enhanced SERS substrate based on critical distance regulation

Abstract

The invention belongs to the technical field of nanophotonics and spectrum detection, and particularly relates to a preparation method and application of an LSPR enhanced SERS substrate based on critical distance regulation. The core of the LSPR enhanced SERS substrate is that the shortest surface spacing between the silver nanoparticle pairs on the substrate carrier is precisely controlled to be 0.5-5.0 nm, particularly near the critical value of 3.0 nm, the strongest coupling LSPR effect can be excited, and the electromagnetic field enhancement factor reaches the peak value. The invention breaks through the technical bottleneck that the traditional SERS substrate has random hot spots and low enhancement efficiency, and realizes the cooperative improvement of the sensitivity, reproducibility and stability of the SERS substrate through the quantitative interval design. The preparation method realizes accurate control of the shortest surface spacing by means of regulating and controlling self-assembly conditions, using molecular spacing arms and the like. The SERS substrate can be used for high-sensitivity and rapid detection of trace substances such as environmental pollutants, biomolecules and the like.

Inventors

• YANG YANQIU
• DING JIACHENG
• SONG PENG

Assignees

• 辽宁大学

Dates

Publication Date

20260512

Application Date

20251204

Claims (10)

1. 1. The LSPR enhanced SERS substrate based on critical spacing regulation is characterized by comprising a substrate carrier and a metal nano structure unit fixed on the surface of the substrate carrier, wherein the metal nano structure unit comprises at least one pair of metal nano particles, the shortest surface spacing d between two metal nano particles of each pair of metal nano particles is 0.5 nm-5.0 nm when the metal nano particles are silver nano particles, the shortest surface spacing d between two metal nano particles of each pair of metal nano particles is 8-nm-15-nm when the metal nano particles are silver-gold core-shell structure nano particles, and the electromagnetic enhancement factor of the metal nano particle pair has a maximum value along with the change of the spacing d within the range of the spacing d.
2. 2. The LSPR enhanced SERS substrate based on critical spacing modulation of claim 1, wherein the substrate carrier is a silicon wafer, glass, indium tin oxide conductive glass, or a flexible polymer film.
3. 3. The LSPR enhanced SERS substrate based on critical spacing modulation of claim 1, wherein the metal nanoparticles are spherical, cubic, rod-like or polyhedral in shape, and the metal nanoparticles have a particle size of 50 nm to 150 nm.
4. 4. The LSPR enhanced SERS substrate based on critical spacing modulation of claim 1, wherein when the metal nanoparticles are silver nanoparticles, a shortest surface spacing d between two metal nanoparticles of each pair of metal nanoparticles is 3.0 nm ±0.5 nm.
5. 5. A method for preparing an LSPR enhanced SERS substrate based on critical spacing modulation as claimed in any of claims 1 to 4, comprising the steps of: 1) The substrate pretreatment, namely cleaning and surface activating the substrate carrier to strengthen the binding force of the substrate carrier and the metal nano particles; 2) The metal nano particles are modified, namely the metal nano particles are fixed on the surface of the pretreated substrate carrier through a chemical self-assembly method, an electrostatic adsorption method or a template auxiliary method to form monolayer or sub-monolayer distribution; 3) The shortest surface distance d is precisely regulated by precisely controlling the technological parameters in the step 2), when the metal nano particles are silver nano particles, d falls into the range of 0.5-5.0 nm, and when the metal nano particles are silver-gold core-shell structure nano particles, d falls into the range of 8-15 nm.
6. 6. The method of claim 5, wherein the controlled process parameters include concentration of nanoparticle suspension, ionic strength, pH, reaction temperature and time, use of bifunctional molecules as spacer arms, geometry of template.
7. 7. The method of claim 6, wherein the bifunctional molecule is DNA or alkyl thiol.
8. 8. Use of an LSPR enhanced SERS substrate based on critical spacing modulation as claimed in any of claims 1 to 4 for detecting trace species.
9. 9. The use of claim 8, wherein the trace species comprise environmental contaminants, biomarkers, explosives, drugs.
10. 10. The use according to claim 8, wherein the detection is performed by contacting the LSPR enhanced SERS substrate with a sample containing the analyte based on critical spacing modulation and then collecting and analyzing the SERS signal using a Raman spectrometer.

Description

Preparation method and application of LSPR enhanced SERS substrate based on critical distance regulation Technical Field The invention belongs to the technical field of nano photonics and spectrum detection, in particular relates to a Surface Enhanced Raman Scattering (SERS) substrate, and particularly relates to a SERS substrate capable of maximizing Local Surface Plasmon Resonance (LSPR) effect and electromagnetic field enhancement by precisely regulating and controlling critical intervals among metal nanoparticles, a controllable preparation method thereof and application thereof in trace substance detection. Background Surface Enhanced Raman Scattering (SERS) technology is a powerful analytical technique that can enhance the raman signal of molecules adsorbed on roughened metal surfaces or nanostructures by millions of times or even more. The enhancement mechanism of this technology is mainly derived from two aspects, electromagnetic Enhancement (EM) and chemical enhancement (CM). Among these, electromagnetic enhancement is the dominant factor, the physical nature of which is the Localized Surface Plasmon Resonance (LSPR) effect, i.e., when the frequency of incident light matches the collective oscillation frequency of free electrons in a metal nanostructure, a highly localized enhanced electromagnetic field is created near the nanostructure surface, these areas being referred to as "hot spots" (Hot Spots). Among the numerous SERS substrate materials, silver nanoparticles (Ag NPs) are widely studied for their strong and tunable LSPR effect in the visible region, high electric field enhancement factors, and relatively mature preparation processes. Both theory and practice have demonstrated that when two or more metal nanoparticles are brought into close proximity with each other, the gap region creates a coupled LSPR effect, resulting in an order of magnitude increase in electromagnetic field strength, such gap being one of the most efficient "hot spots". However, there is a significant bottleneck in the prior art that the regulation of nanoparticle gaps is dependent on empirical attempts, lacking a profound understanding and precise control of the quantitative, non-linear relationship between gap size and electromagnetic field enhancement. Most studies only qualitatively indicate "smaller, better", but do not reveal their inherent non-linear laws and critical thresholds. This results in unstable "hot spot" densities and enhancement efficiencies of the prepared SERS substrate, poor reproducibility, and performance that is not at theoretical optimum. Furthermore, too much pursuing a very small pitch (e.g., <1 nm) tends to trigger uncontrolled agglomeration of nanoparticles, rather leading to a broad LSPR peak, an increased energy dissipation, and poor stability in practical applications. Therefore, there is an urgent need in the art for a method capable of precisely guiding and implementing controllable construction of nanoparticle spacing, and a SERS substrate developed based on the method and having a known, optimal and stable gap "hot spot", so as to solve the problem that the sensitivity, reproducibility and stability of the existing SERS technology are difficult to be compatible. Disclosure of Invention In view of the above-mentioned drawbacks of the prior art, a primary object of the present invention is to provide a SERS substrate with ultra-high and stable electromagnetic field enhancement by constructing metal nanoparticle pairs or clusters with specific critical spacing. Another object of the present invention is to provide a method for preparing the SERS substrate described above, which enables precise and controllable adjustment of the nanoparticle spacing. It is a further object of the present invention to provide the use of the SERS substrate in the detection of trace chemicals, biomolecules and environmental pollutants. In order to achieve the above purpose, the present invention adopts the following technical scheme: The LSPR enhanced SERS substrate based on critical spacing regulation comprises a substrate carrier and a metal nano structure unit fixed on the surface of the substrate carrier, wherein the metal nano structure unit comprises at least one pair of metal nano particles, when the metal nano particles are silver nano particles, the shortest surface distance d between two metal nano particles of each pair of metal nano particles is 0.5 nm-5.0 nm, when the metal nano particles are silver-gold core-shell structure nano particles, the shortest surface distance d between two metal nano particles of each pair of metal nano particles is 8 nm-15 nm, and in the range of the distance d, the electromagnetic enhancement factor |E/E 0|4 of each metal nano particle pair shows a nonlinear change relation of enhancing before attenuating along with the reduction of d. Preferably, the substrate carrier is a silicon wafer, glass, indium Tin Oxide (ITO) conductive glass, or a flexible polymer film.