Optical Properties And Applications Of Core-shell Structured Micro-nano Material

Core-shell structure is a new type of structure.It combines one micro-nano material with another micro-nano material to form a complex structure with unique physical and chemical properties.The structural parameters of core-shell structure nanomaterials are adjustable,which greatly stimulate researchers’interest in the synthesis of core-shell structure micro-nano materials.However,the interaction mechanism,property and function of core-shell are still not clear,which limits its application in optics,biochemistry and other fields.In order to make micro-nano materials with core-shell structure more widely used,in this paper,several different core-shell structure models are designed,their optical properties and applications are analyzed.First,we study the scattering properties of the core-shell structure containing graphene,focusing on electric field distribution,energy density and radiative and nonradiative decay rate properties.The recursive transfer-matrix method（RTMM）is used to calculate the effects of wavelength and dipole emitter location on the spontaneous emission of Au@Si O₂@Graphene（a three-layer core-shell structure whose core is Au,the intermediate dielectric layer is Si O₂,and the shell is of Graphene）.With the increase of the thickness of the intermediate dielectric layer Si O₂,the Purcell factor in the near-field region increases;The Purcell factor decreases with the distance of the dipole emitter from the center of the sphere,realizing the regulation of spontaneous emission.The maximum value of the Purcell factor in the visible light range is realized at 633 nm by optimizing the design.When the thickness of the dielectric layer is fixed,increasing the radius of the model will decrease the Purcell factor instead.Changing the size parameters of model can effectively strengthen the interaction with light waves,which has a good application prospect in the field of solar photothermal.Next,we will study three double-layer core-shell structure models with metal Ag as core andα-Mo O₃ which is under three different crystal axes（x、y、z）as shell.We will observe the wavelength positions of the maximum SERS enhancement in the models.When the total radius of the core-shell structure is constant,change its structural parameters and then study the electric field distribution of the model in the infrared band,and observe the dynamic evolution of SERS enhanced electric field in space.SERS enhancement factor reached 108 orders of magnitude by optimizing the design,which has great application potential in the detection and characterization of a wide range of chemical and biological agents.