DNA Nanostructure-based Assembly Of Nanoplasmonic Structures And Their Optical Properties

In recent years,surface plasmon resonance(SPR)of metal nanostructures has attracted extensive attention and research because of its unique optical properties.When the gap distance of nanoparticles decreases gradually,the interaction between neighboring nanoparticles results in drastic changes in resonance frequency,generating new optical properties,such as local near-field enhancement,Fano resonance,local plasma photothermal effect,and so on.In addition,the size and spatial distribution of plasmonic hot spots are determined by the size and separation spacing of particles.However,the problem of how to arrange metal nanoparticles exactly on nanometer scale remains to be solved.At present,the preparation methods of metal nanostructures are usually divided into the top-down method represented by etching and the bottom-up method represented by self-assembly.However,the traditional assembly method is difficult to realize the accurate control of nanoparticles.DNA nanotechnology,especially DNA origami,has the advantages of sequence programmability,structural functional diversity and site-addressability,and is widely used for assembling the plasma nanoparticles and become an excellent template for accurately controlling the nanoparticles under the nano-scale.Based on DNA origami-assembled anisotropic gold nanoparticles(Au NCs,Au NRs),the optical properties of gold nanostructures produced by plasmon resonance are systematically studied in this thesis.First,the nano-gold cube dimers were designed and assembled to study the properties of the enhanced Raman signal,secondly,the nano-gold cube and gold rod dimers were designed and assembled to study the Fano resonance effect produced by its structure.Finally,the Fano resonance effect of the nanorod "Dolmen" structures were further studied by designing and assembling the nanorods.The results are as follows:The nanometer gold cubic dimers were designed and assembled to study the properties of the nano-gold cubic dimers in the field of enhanced Raman signal;Secondly,we designed and assembled the nano-gold cube and gold rod dimer to study the Fano resonance effect produced by its structure;Finally,we designed and assembled the "Dolmen" structure of the gold nanorod to further study the Fano resonance effect produced by the structure,as follows:1.Three dimer configurations,FTF(face to face),FTS(face to side)and STS(side to side),were formed by using DNA origami technique and nano-gold cubic modification by designing the self-assembly of the extended capture sites on origami.The Raman enhancement signals of three gold-cube-dimer structures were collected by SEM and DFM,and the Raman enhancement factors(EF)of the three configurations were calculated to study the effect of configuration changes on the surface plasmon resonance(SPR)properties.The detection of single particle SERS signal is successfully realized.2.On the basis of the study of homogeneous assembly structure in the previous chapter,two heterogeneous dimer configurations were formed by using DNA origami technique and nano-gold cube and gold rod modification by self-assembly of extended capture sites on origami: "face-rod" and "edge-rod" nanostructures,respectively.The scattering spectra of the target structure are collected by SEM and DFM co-location.According to the different morphology of the assembled gold nanoparticles,the influence of them on the Fano resonance effect is studied.The scattering spectra of the target structures were co-located by SEM and DFM,and the nostive resonance effect was studied.3.In order to investigate whether the change of assembly configuration between gold nanoparticles has an effect on the Fano resonance effect,we have systematically studied the assembly structure of gold nanorods.The "Dolmen" structure which was assembled by a gold nanorod and a parallel double-rod dimer on both sides of the DNA origami paper was formed by self-assembly of rectangular DNA origami with gold nanorods.The scattering spectra of the structure were co-located by SEM and DFM and the electric field distribution of the structure was simulated by finite-difference time-domain(FDTD)to study the Fano resonance effect.Then,two structures with different relative angles,"right Dolmen(RD)" and "left Dolmen(LD)",are investigated to explore the effect of plasmonic coupling on the relative angle of a single gold rod relative to the dimer of a parallel gold rod.In this thesis,we systematically study the DNA nanostructure-mediated nano-plasmonic structures assembly and the optical properties,and provide a new idea for how to further realize the local near-field enhancement.It also lays a foundation for exploring the Fano resonance effect of symmetry broken structure.