The Preparation Of Optical Artificial Microstructure And Its Application In Biological Detection

Food safety is related to the national economy and people’s livelihood.A wide variety of pesticides and excessive use of heavy metals directly endanger people’s health.In order to improve food safety,it is an urgent task to develop a rapid and efficient pesticide detection technology.At present,the existing detection technologies for agricultural residues are various and have their own advantages and disadvantages.We mainly take microstructure as the carrier for research.Microstructures refer to structures with dimensions reaching nanometer level,and exhibiting specific functions or properties that macro structures do not have.Microstructures mainly include photonic crystals and metamaterials.Metamaterial is an artificial composite material with extraordinary physical properties that natural materials do not have.It is formed by arranging sub-wavelength resonant units according to a special macro sequence,and its working wave is longer than its structural size.The electromagnetic field and optical modes（e.g.magnetic plasma resonance、bragg diffraction etc.）can be controlled by changing the structure of metamaterials.Magnetic resonance mode is very sensitive to the changes of refractive index of the surrounding environment,so heavy metals or pesticides can be loaded into metamaterial structures in a specific way,and dynamic monitoring of heavy metals and pesticides with different types and concentrations can be realized through testing absorption spectras.The main tasks are the following:（1）Silver nanoparticles are synthesized by thermochemical method,and their intrinsic absorption peak,that is,the surface plasmon resonance of silver nanoparticles,can be obtained by testing absorption spectras..Dropping different kinds and concentrations of heavy metal ions into silver nanoparticles can have different effects on their surface plasmon resonance,and effective monitoring of heavy metals can be realized through absorption spectrum testing.（2）Metal-dielectric-metal is an important configuration of metamaterials.The structure ofAg-SiO₂-Ag is established by modeling and simulation,and the influence of dielectric duty factor on optical modes in the structure are studied.Dielectric duty factor is related to dielectric thickness and grating size and plays a vital role in magnetic resonance.Through the analysis of electromagnetic field distribution and data fitting,the phase change law and the correlation law of duty cycle are obtained.（3）By mixing pesticides with different concentrations in polyimide solution,spin-coating the mixed solutions on Au films respectively,and then spin-coating single-layer polystyrene microspheres on the surface.The detection of pesticides are realized through the test of reflection spectrum.