Design Of Metal-medium Structural Materials And Application Research In Pesticide Residue And Heavy Metal Detection

With the development of micro-processing technology,optical metamaterials have received increasingly attention in both research and industry.The structure of metal-dielectic is important unit cell in metamaterials,where photons and electrons can combine perfectly,then Surface Plasmon Polariton?SPP?can be excited at the metal-dielectric interface.Furthermore,the antiparallel Surface Plasmon Polaritons may occur at the up metal-dielectric and down dielectric-metal interface,magnetic dipole resonance is introduced.Large electromagnetic fields are localized in the dielectric layer,which will enhance the interaction between light and structure.The excessive usage of organophosphorus pesticides and heavy metals have posed a great threat to human life.Therefore,we propose to use metal-dielectric structural materials as medium in optical detection,it can overcome the problems of complicated operation,high detection and inability to detect in real time etc.In this paper,the metal-dielectric-metal metasurface in visible-infrared band is studied by simulation and experiments.And then we study the detection of organophosphorus pesticide trichlorfon and heavy metal Hg²⁺using metal-dielectric structural materials.The thesiscontain 3 parts,as follows:1.In visible,we fabricated sample of Au/SiO₂/Au periodic nanoparticle arrays by using soft X-ray Interference Lithography?XIL?and assisted processes.Both the experiment and simulation results show that the absorption peaks of the array in spectra comes from Fabry-Perot?F-P?cavity mode and Fano resonance formed in metasurface.2.In infrared,on the basis of structural design,we designed a series of Ag/SiN/Ag with square Ag patches on the topmost laye.By changing the side lengths of patches,the location of resonant peaks can be altered.Furthermore,the anisotropic properties can also be modulated by changing the side length in x-and y-direction.Using the maskless lithography technique,we fabricated the designed samples.The absorption spectrum evidenced that Ag/SiN/Ag metasurface possess strong absorption,polarization selectivity and arbitrary adjustability.Using commercial software FDTD Solutions,the electric and magnetic field distributions of the magnetic dipole resonance and phonon modes were analyzed,and the physical mechanism of the polarization selectivity was given.3.The metal-dielectric structural materials are used as a carrier to realize the detection of organophosphorus pesticides and heavy metals in the visible-infrared band.With addition Trichlorfen pesticides into polyimide in Au/polyimide and Au/polyimide/polystyrene sphere system,the detection limit can reach to5?10^-5mol/l,due to the polystyrene sphere on the Au-polyimide interface.With HgCl₂ solutions of different concentrations drop wised onto Au/SiO₂/Au nanoparticles array,the trace detection of heavy metal Hg²⁺realize,and the detection limit reachn?28?1?10^{-1 5}mol.Infrared spectra can be used as fingerprint of materials.Through analysis the absorption spectra of trichlorfon,we designed Ag/SiN/Ag particle configuration,whose absorption peak come from magnetic dipole resonance can couple with that of trichlorfn molecule,thereby,it can enhance the interaction of light and the trichlorfon molecule.High sensitivity detection of trichlorfon achieved.