Electromagnetic "Hotspots" Regulation And Its Surface Enhanced Raman Scattering Applications

The surface-enhanced Raman scattering(SERS)technique allows label-free detection and analysis of detected molecules through fingerprint information of molecular vibrations and is widely used in food safety,environmental monitoring,medical diagnosis,etc.Based on the powerful detection and analysis capabilities of SERS technology,the preparation of SERS substrates with easy handling and excellent performance(sensitivity,uniformity,reproducibility,and practicality)has become a tireless goal for researchers.In recent years,researchers have made efforts to design and prepare various efficient SERS substrates with abundant hot spots that have evolved from the initial studies of rough electrode model systems to the highly complex studies of today.but the conventional SERS substrates mainly generate hot spots in a point-to-point or point-to-face manner,which leads to a very small proportion of the effective area that can be reached or adsorbed by the band test molecules.In this paper,two new SERS substrate structures have been designed based on existing research using two-dimensional material graphene as a spacer layer,which greatly improves the utilization of SERS substrate structures for space and incident light.The specific work is as follows:(1)We propose the FWPS with graphene as the spacer layer and investigate the thickness of the metal film for the optimal SERS effect,which greatly improves the spatial occupation of the hot spot.The optimal fabrication conditions and performance of the system were investigated by the theoretical simulation software COMSOL Multiphysics.The simulation results show that a strong large-scale local electromagnetic field appears throughout the space between the Ag nanoparticles and the Au film.The experimental results show that the FWPS SERS substrate exhibits excellent sensitivity(crystal violet(CV): 10-11 M),uniformity,stability and high enhancement factor(EF: 2.23 × 108).Malachite green(MG;10-10 M)and DNA strands of different base sequences(A,T,C)were successfully detected on the surface of the fish.The results of these assays indicate that the FWPS SERS substrate has a high prospect of application in the detection of environmental contamination and biomolecules.(2)A simple and productive SERS substrate structure was designed by preparing firstly anodic alumina by electrochemical method as a substrate supporter,and then sequentially transferring graphene and depositing Au nanoparticles on the alumina supporter to form Au NPs/graphene/bowl-shaped Al2O3 bowl-shaped complex SERS substrates.The Au NPs/graphene/bowl-shaped Al2O3 bowl-shaped complex arrays exhibit excellent SERS performance due to their special structural features and strong anti-reflectivity,which increases the utilization of incident light.Theoretical simulation results show that the Au NPs/graphene/ bowl-shaped Al2O3 structure increases the electric field intensity by 96.1times compared to the flat substrate support The proposed Al2O3 bowl-shaped composite array structure provides a new idea for the design of SERS substrates and shows great potential for applications.