DNA Nanostructure-based Assembly Of Metal Nanoparticles And Their Surface Enhanced Raman Scattering

Since metal nanoparticles have unique optical properties,self-assembly of metal nanostructures has attracted widespread attention and show great progress.Metal nanostructures with different chemical compositions,different shapes and sizes have been precisely arranged to form a nanostructure with plasmonic effect.These nanostructures exhibit unique spectral characteristics such as circular dichroism(CD),surface-enhanced Raman(SERS),and ultraviolet-visible spectrometry(UV-VIS).These plasmonic nanostructures can be widely used in energy collection and biosensing.Top-down approaches such as lithography are the typical methods to assemble metal particles.But they still exist sone challenges including making three-dimensional structures and cost-effective mass production.DNA-based self-assembly technology provides a bottom-up rapid assembly way to construct highly coordinated nanostructures.Because of their unique self-recognition properties and high precise addressability,DNA nanostructures are employed as templates to self-assemble plasmonic nanostructures.In this thesis,we designed and fabricated three special DNA nanostructures as templates for the organization of gold nanoparticles(Au NPs).Thus prepared Au NPs nanostructures showed enhanced SERS performance.Based on the above content,the research content of this paper is divided into the following three aspects:1.To increase the organizing yield of the ss DNA fully modified Au NPs to the DNA origami templates,one key point is to weaken the charge repulsion between them.We used a cavity-type DNA origami as the template for the programmed positioning of 30 nm Au NPs Transmission electron microscopy(TEM)images showed that high yields of dimer and tetramer plasmonic nanostructures were obtained by using the cavity-type DNA origami as the template.More importantly,we observed significant Raman signal enhancement from molecules covalently attached to the plasmonic nanostructures,which provides a new way to high-sensitivity Raman sensing.2.DNA origami nanostructures need a long scaffold DNA with hundreds of staples and the time-consuming annealing procedure.Here,we designed a novel DNA nanoribbon which formed by four DNA stands with room-temperature annealing in 20 minutes.One-pot reaction was used to assemble gold nanoparticles(10 nm-,20 nm-,30 nm-sized)into a linear nanochain.These Au NPs nanochians owned intense hot spots in the gaps of Au NPs which enhanced the SERS signal of 4-MBA molecules.3.A two-dimensional DNA nanostructure were designed by five DNA strands.A surface-assisted assembly approach was used to form the two-dimensional DNA nanostructures in micrometer scale.In addition,two-dimensional DNA nanostructures at specific sites out of the capture chain to fix the 5 nm Au NPs to form a high-density two-dimensional array of Au NPs.This method can be widely used in the manufacture of nano-sized integrated circuits,and the formation of two-dimensional metal nanostructures has great potential in the field of excellent SERS research.