| Noble metal nanomaterials exhibit excellent photoelectric properties due to their unique surface plasmon resonance properties,exhibiting a wide range of applications in material science,life science and nano-photonics.Silver nanostructures show excellent optical properties,such as sharp absorption bands and tunable resonance peak position,which has receivedbroad attention.In this thesis,the optical property of silver nanoparticles coated with thiol-terminated polystyrene were systematically studied.Firstly,silver nanoparticles coated with thiol-terminated polystyrene ligands of different lengths were synthesized.Then these silver nanoparticles were self-assembled into nanoparticle superlattice film and the optical property of the film were investigated.Furthermore,the chiral assemblies of silver nanoparticle from co-assembly of silver nanoparticle functionalized with thiol-terminated polystyrene and π-conjugated chiral molecules were fabricated and studied.The asymmetry ofπ-conjugated chiral molecules is transferred to the assemblies of plasmonic silver nanoparticles via CH-π interaction.The detailed research contents are as follows:(1)Synthesis of silver nanoparticles coated with thiol-terminated polystyrene ligands of different lengths:The silver nanoparticles coated with oleyamine were synthesized by a onepot method.Silver nanoparticles coated with thiol-terminated polystyrene ligands of different lengths were prepared by a ligand exchange method and the number-average molecular weight(Mn)of polystyrene ligands varies from 2.4 to 15.9 kg mol-1.The Ag-S covalent bond significantly improves the chemical stability of silver nanoparticles,which is of fundamentally importance for the self-assembly and co-assembly of silver nanoparticles.(2)Optical properties of Ag@PSMn nanoparticles superlattices:The 9.8 nm silver nanoparticles coated with thiol-terminated polystyrene ligands were self-assembled by solvent evaporation method,which produced a highly ordered crack-free nanoparticle superlattice film,and the interparticle gaps can be tuned ranging from 4.1 to 15.3 nm.Moreover,the optical properties of these Ag@PSMn nanoparticle superlattice film were studied by using a microspectrophotometer and FDTD numerical simulations,elucidating the relationship between the interparticle gap and the plasmonic coupling effect in silver nanoparticle superlattices.This work has important implications for regulating the optical properties of silver nanoparticle superlattices by precisely adjusting the Mn of surface-coated polymers.(3)Optical properties of the silver nanoparticles and chiral molecules co-assemblies:The 1,3,5-triphenylbenzenetricarbox-amides(TPBAs)chiral molecules were designed and synthesized as the building block for supramolecular polymerization.These molecules have strong π-π interactions,hydrogen bonding and van der Waals interactions,which can be used as an ideal template for constructing chiral co-assemblies with nanoparticles.The chiral molecules and silver nanoparticles were co-assembled by the emulsion-confined method.CHπ interaction,one of the weakest hydrogen bonds,are used to transfer the asymmetry of πconjugated chiral molecules to the assembly of plasmonic silver nanoparticles.The aliphatic chain of chiral molecules and the polystyrene chain coated on the nanoparticles are served as hydrogen donor and acceptor,respectively.The results show that the optical dissymmetry gfactor of the chiral assemblies of silver plasmonic nanoparticles strongly depends on the polystyrene ligand’s molecular weight,the molecule’s core structure,and the aliphatic chain length of chiral molecule.Importantly,the molecular mixing strategy are explored to enhance the dissymmetry g-factor of chiral molecular assemblies,which reaches a high value of～0.05 under optimal conditions.Overall,the transfer of chirality from organic molecules to inorganic nanoparticles are explained,which provides the guidance for the structural design of high g-factor chiral nanocomposites. |
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