Directional Templating Mechanisms of Anisotropic Nanoparticles Using Poly(pyromellitic dianhydride-p-phenylenediamine)

This study reports for the first time the use of poly(pyromellitic dianhydride-p-phenylenediamine) (PPDD) as a reducing and stabilizing agent, immobilization matrix, and directional template for the synthesis of anisotropic silver nanoparticles (AgNPs). The work also provides a new,physical insight into the mechanisms of directional templating of anisotropic nanoparticles based on diffusion-limited aggregate model and coalescence :growth mechanism. Molecular dynamics simulations and density functional theory calculations were performed to provide insight into,possible conformations of the PPDD monomer. Anisotropic (nonspherical) peanut-shaped nanorods and dendritic nanostructures were prepared in situ using, varying concentrations of precursors from 0.1 to 1.0% w/v within PPDD matrix. The PPDD served as the reducing and directional template, thus enforcing preferential orientation. The mechanism of formation and growth of the polymer-mediated anisotropic nanoparticles was confirmed using transmission electron microscopy, UV-vis near-infrared absorption spectra (UV-vis-NIR); and X-ray diffraction, The size distribution Of the nanoparticles was found to be 6-10 (0.1% w/v), 20 (0.2% w/v),. and 70-100 nm (0.5% w/v). The UV-vis-NIR spectra confirmed the existence of-transverse and longitudinal-surface plasmon resonance according to Mie theory. The anisotropic growth of dendritic/nanorods AgNPs could be attributed to diffusion-limited aggregate:, model and coalescence growth mechanism. 111 planes were the most predominant structures, indicating inhibition of-growth along the perpendicular axis by PPDD, thus conferring the preferred coalescence-orientation of nanopartide parallel on the film.