Ligand-Assisted Synthesis of Plasmonic Ag Nanowires: A Molecular Dynamics Study on Anisotropic Growth

This study demonstrates a solution-phase polyvinylpyrrolidone (PVP)-assisted approach to prepare shape-controlled plasmonic Ag nanostructures in ethylene glycol (EG) solution via heterogeneous nucleation (in the presence of FeCl3). Combining with experimental study, molecular dynamics (MD) simulation is also used to understand the underlying principles governing nanowire growth through the analysis of the interaction energies between crystal surfaces and capping agent as well as atom density profile. The simulation results indicate that the PVP concentration, as a capping ligand and shape-directing agent, plays a key role in the anisotropic confinements during growth process of nanowires because the interaction energy between PVP molecules and silver crystals (through Ag : O coordination) on (100) and (110) planes is stronger, which leads to oriented attachment of crystals and the anisotropic growth on the (111) planes. Furthermore, the plasmonic properties of the as-synthesized nanowires are confirmed by UV-Visible spectra displaying a dual-peak absorption ascribed to the transverse dipole resonance (longer wavelength, λ=420 nm) and the transverse quadrupole resonance (shorter wavelength, λ=380 nm).