The Application Of Metal Nanostructures In Nanoruler And SERS Based On Fano Resonance

Surface plasmons(SPs)have attracted much attention due to their ability to manipulate light at nanoscale and their extensive applications in chemical and biological sensing.The surface plasmon is very sensitive to the change of geometric parameters and the dielectric environment of metal nanostructures.Besides,strong local electric field can be excited around the metal nanostructures.However,the SPs has been widely applied in the field of chemical and biological sensor,surface enhanced Raman scattering(SERS),fluorescence enhancement and many other fields.In this paper,the applications in nanruler and SERS of the metal nanostructures based on Fano resonance was investigated.The metal nanostructures based on Fano resonance can support a narrow line-width and in more sensitive to the change of geometric parameters.Besides,stronger local electric field can be motivated so that the Fano resonance can enhance the detection sensitivity of nanoruler and the intensity of SERS.The main completed work is as follow:(1)The general nanoruler are based on the surface plasmon resonance(SPR).It can distinguish the change of biological macromolecules in the nanoscale range by the shifts of the resonance peak.However,because of its wide line width,when the distance or parameters of the nanostructure change,the shifts of spectrum is not obvious,which lead to its low sensitivity.Compared to the general plasmon resonance,Fano resonance can support an SPR with a narrow line-width,which causes the spectral shift to be more sensitive to the distance between nanostructures.In this paper,we designed a 2D distance and rotation angle plasmon ruler based on Fano resonance of a trimer nanostructure,which consists of a concentric square nanoring-disk and an outside nanorod(CSRDR).The Fano dip energy and depth are fairly sensitive to the nanometer-scale displacements and rotations,when the nanodisk moves in all direction and rotates around its center.The Fano dip changes 0.05eV when moving in a horizontal direction,which sensitivity is 3-4 times more than other rulers.The Fano dip change 0.025eV and 0.08eV when moving in a vertical direction and rotate with different angles.When the symmetry of the nanoring is broken,we can identify the moving and rotating direction of the nanodisk more accurately.We use the CSRDR nanostructure which supports a narrow line-width as a 2D plasmon ruler,which can enhance the sensitivity of a plasmon ruler significantly.(2)The second work is mainly studied the Fano resonance supported by nanorod-rod and double nanospheres structures.When the length and nanorod thickness of the metal structure change,the Fano dip will move accordingly.According to this law,we adjusted the Fano resonance wavelength to the Raman laser with 633 nm,which provided good guidance for our relevant experiments.We also studied and properties of the asymmetry double nanospheres.Then we get the electric field distribution and the scattering spectrum through changing the diameter of spheres and the distance between two spheres.Though the electric field distribution we found that with the decrease of the diameter,the number of "hot spots" of Raman enhancement increased.Then we fabricated the SERS substrate with Au double nanospheres which fabricated by annealing method,and with rhodamine 6G(R6G)with different concentrations as the analyte,the SERS effect was investigated.As the experimental results suggest,the double nanospheres can enhance the intensity of SERS signals.