DNA-programmed Spatial Arrangement Of Nanoplasmonic Structures

Metallic nanostructures that support surface plasmons have been widely applied to nanophotonics,biological imaging,nanomedicine.The plasma properties of metallic nanostructures are closely related to their size,morphology,composition and interparticle plasmon coupling.However,it is still a great challenge to precisely control the geometric shape and spatial arrangement of metal nanoparticles,which can realize the plasma nanostructures with well-defined configurations and tailored optical functionalities.DNA as the main carrier of genetic information,recently has been widely studied as versatile nanomaterials.With the development of DNA nanotechnology,DNA molecules or DNA nanostructures as the template,have been widely used in assembly and growth of nanoplasmonic structures.Depending on its highly programmability,sequence specificity and adjustable length,DNA can provide a powerful way for achieving precise spatial arrangement of nanoparticles and fine control over nanoparticle's morphology.In the present thesis,we explored the assembly of plasma nanomaterials and the synthesis of metal nanostructures with specific morphology by using DNA as a template.The research content mainly includes two parts: the first part is that DNA encodes the valence bond,bond energy and bond length on the surface of the nano-gold particles to realize the assembly of complex plasmonic nanomaterials,including chapters 2 and 3;the second part is that DNA regulates the growth of gold nanostructures using GD as a template to achieve the synthesis of metal nanostructures with specific morphology,including chapter 4.In the 2nd chapter,during constructing the complex plasmonic nanostructures,the valence bond information of the DNA ligands on AuNPs surface directly affects the spatial arrangement of AuNPs.This thesis constructed a one-step method for programming valence bonds on the surface of gold nanoparticles using single-stranded DNA coders to achieve precise assembly of metal nano-particles in space.We designed a general single-stranded DNA encoder(SSE)approach for programming valence bonds of AuNPs in one step.We used multi-block single-stranded DNA sequences to encode the valence bond information on the surface of gold nanoparticles,and then constructed colloidal atoms with discrete valence and orthogonal valence bonds.With these colloidal atoms as the primitives,colloidal molecules with precise particle number and anisotropy can be formed by orthogonal DNA pairing self-assembly.And these colloidal molecules still have the ability to undergo post-synthetic rearrangement.Therefore,DNA strand-displacement reactions can trigger dynamic bond-formation and bond-breaking to simulate various basic chemical reactions such as condensation,dissociation,replacement,and redecomposition.Based on this system,we also designed single-particle logic gates and integrated them into "voting machine" logic circuits.These precisely assembled nano-atoms and molecules with dynamic response capabilities are expected to be used in bio-intelligent diagnosis and treatment.In the 3rd chapter,DNA-functionalized Au nanoparticles have been intensively exploited as programmable atom equivalents(PAEs)for self-assembly of molecule-like structures.However,it remains challenging to build hierarchical PAE assemblies via discrete DNA bonds at different levels.We designed a method to program DNA bond length and bond energy on programmable atom equivalents(PAEs)using DNA encoders.On Au nanoparticles,we built three types of DNA motifs with different topological configurations,which can serve as bonds for PAE self-assembly.By smallangle X-ray scattering(SAXS)analysis,we found that the bond length between the coupled PAEs can be tuned by programming the bond structure.We also found that these bonds show different bond energies dependent on their topologic configuration.We demonstrated that the differently-levelled bonds can be arranged at different directions on one nanoparticle,leading to asymmetric PAEs which allowed for ionic strength-controlled hierarchical assembly of multi-particle structures.This programmable bonding system may provide a new route for building complex plasmonic superstructures.In the 4th chapter,in the process of synthesis metal nanostructures with specific morphology,it is still of great significance to develop a simple and rapid method for synthesizing the plasmonic nanostructures with adjustable geometry and shape.We reported the use of multi-layered GD as a substrate for the reductant-free,roomtemperature synthesis of single-crystal Au nanostructures with tunable morphology.We found that the GD template rich of sp-carbon atoms possessed high affinity with Au atoms on the {111} facets,and that the intrinsic reductivity of GD facilitated the rapid growth of Au nanoplates.The introduction of single-stranded DNA strands further resulted in the synthesis of Au nanostructures with decreased anisotropy,i.e.,polygons and flower-like nanoparticles.The DNA-guided tunable Au growth arises from the strong adsorption of DNA on the GD template that alters the uniformity of the interface,which provides a direct route to synthesize Au nanostructures with tailorable morphology and photonic properties.In summary,this dissertation firstly constructed a new strategy to precisely control the valence bonds on the surface of Au nanoparticle by using the non-covalent interaction between single-stranded DNA and nanoparticles,which can fabricate orthogonal artificial nano-atoms and reconfigurable colloidal molecules and provide a new idea for assembling multi-responsive biomedical functional materials;secondly,we reported a method to encode the DNA bond length and bond energy on the surface of AuNPs based on the non-covalent interaction between single-stranded DNA and nanoparticles,which provided a new strategy for hierarchical assembly of complex plasmonic nanostructures;finally,we synthesized anisotropic Au nanostructures by using DNA to regulate the uniformity of the growth template GD interface,which is of guiding significance for the rapid synthesis of Au nanostructures with tailorable morphology and optical properties.