Study On Optical Properties Of Spherical Nanoparticles By Mie Theory

Nanoparticles have significant research value in the development of modern science.They can be used in the fields of catalysis,generation of surface plasmas,bio-detection and preparation of metasurfaces.The characteristics of nanoparticles can be analyzed by studying their absorption properties and scattering properties.Therefore,in order to select nanoparticles with specific characteristics,the research of variation patterns of nanoparticles is vital.Analytical and numerical methods can be used in the research of nanoparticles.This research is based on the Mie theory,which is an analytical method.The calculation process of Mie theory is studied.By deriving the Mie coefficients for spherical particles in a double-layer medium with a shell-core structure and organize the recursive algorithm for calculating the Mie coefficients,the Mie coefficients for homogeneous spherical nanoparticles and nanoparticles with multilayer shell structures would be calculated quickly and accurately.By analyzing the correspondence between the Bessel function and the relative size parameter from calculation,the recursive algorithm can be implemented.According to the recursive algorithm,the program was written by using MATLAB.And use the program to analyze the properties of nanoparticle.The program of the recursive algorithm is used to analyze the scattering efficiency,absorption efficiency and extinction efficiency of homogeneous spherical nanoparticles and shell-core structured spherical nanoparticles.These efficiencies are influenced by the real part of the refractive index,the relative size parameter and the imaginary part of the refractive index.According to the analysis,the real part of the refractive index corresponding to homogeneous spherical nanoparticles can modulate the waveforms and the position of peaks.They vary with relative size parameters.As for shell-core structured spherical nanoparticles,the peaks of the scattering efficiency are modulated by the radius of the shell and the core.When the shell radius increases,the changes of peak are similar to homogeneous spherical nanoparticles.The peaks of scattering efficiency change again when the core radius increases.The real part of the refractive index is found to modulate the frequency and range of the occurrence of the Mie coefficients.And the relative size parameter changes the number and contribution of the occurring Mie coefficients.So,the scattering efficiency fluctuates and many peaks occur.As for the shell-core structure,the Mie coefficient is also affected by the radius of shell and core.After the introduction of the imaginary part of the refractive index,there is a different variation.The imaginary part of the refractive index will make the peaks of the Mie coefficient separated.The peaks appear at the different time and lead the scattering efficiency,absorption efficiency and extinction efficiency to become stable.At the same time,the size of the imaginary part affects the size of the scattering efficiency and the absorption efficiency.And they vary differently.When the imaginary part increases,the scattering efficiency increases.At the same time,the absorption efficiency decreases.Finally,the effect of local surface plasmon resonance is analyzed for the shell-core structured nanoparticles by using a combination of Ag and Ga As to simulate.Through the analysis of the Mie coefficients,it is found that with the changes of size of the shell and the core,different Mie coefficients change differently.Then,the scattering efficiency and absorption efficiency change differently.By analyzing the effect of surrounding media with different refractive indices on the extinction efficiency of Ag/Ga As nanoparticles,it is found that the change of refractive index of surrounding media is obvious to be detected.The increase of the size of the shell and the core can make the detection peak red-shift and the sensitivity degree decreases.