FDTD Simulation And Design About The Raman Enhancive Basal

Surface enhanced Raman scattering(SERS)has appreciable universality for molecules and interfaces,and it can give information about the structure of matter at molecular level.SERS can be used to detect an aqueous solution or a solid,liquid or gaseous state.It has been widely used in many fields such as biology,chemistry,materials and so on.SERS relies on the substrate activity enhancing the Raman signals of the substrate.The Raman signal of the SERS active substrate is mainly divided into electromagnetic mechanism and chemical mechanism.The electromagnetic mechanism mainly studies the local electric field enhancement,without selectivity.The chemical mechanism is mainly focused on surface adsorption.Based on the active substrate structure of metal nanoparticles,the relationship between metal plasmon and particle size and particle spacing and combined with the dispersion model of metal medium,This has investigated the excitation of light field and the substrate material and simulated the electromagnetic energy distribution of metal nanoparticles under external excitation field by software.Then the cause of local electromagnetic enhancement is analyzed.Finally a simulation model is designed to calculate the enhancement effect of the substrate,according to the existing Raman substrate preparation scheme.The initial background of this paper is the biological cell detection,the Raman enhanced substrate is designed as the core of Raman enhancement technology,as well as the substrate is optimized by FDTD simulation.The purpose of this research is to design the most suitable Raman enhancement substrate for different Raman detection requirements.The research area is the SERS active substrate with the enhancement carrier,particularly metal nanoparticles.The metal nanoparticles will produce localized surface plasmon resonance in the excitation source,enhance the local electric field,the increase electric field in adhesion around marker particle surface,in order to achieve the purpose of enhanced Raman signal.The main contentof this paper is composed of the following four parts:(a)Surface plasmon polaritons and excitation light source impact on nano spherical particles.The nano-metal substrate with a single spherical particle or two dimers of spherical particles is the smallest unit of SERS nanoparticles,surface plasmon polaritons close connection to the incident light and the polaritons form.This has selected the optimum design scheme by simulating the electromagnetic enhancement effect of nanoparticles under different conditions.(two)the red cell scattering field;the designed project in this paper is mainly used for biological Raman detection.Therefore,the scattering field and extincting light characteristics of red blood cells are specially simulated.The scattering field changes caused by refractive index or shape change of red blood cells were simulated by using ellipsoid model and double concave model,which could be used as reference for the pathological changes of erythrocytes.(three)the simulation and design of the SERS substrate.In view of the inhomogeneity of the nanoparticles prepared by chemical synthesis,a random particle model is designed to simulate the actual enhancement effect.According to the requirements of biological detection,a gold nano layer covered silver nano layer SERS substrate model was designed.(four)the origin of metal nanoparticles plasmon polaritons was investigated.By referring to the effect of software simulation and the control variable method,the generation and annihilation process of surface plasmon polaritons is obtained.