Probing the initial stages of molecular organization of oligo(p-phenylenevinylene) assemblies with monolayer protected gold nanoparticles

Abstract

Tapes, fibrils, and fibers: Thiol-protected gold nanoparticles have been used to probe the initial stages of the molecular organization of oligo(p-phenylenevinylene) gelators. The oligo(p-phenylenevinylene) molecules self-assemble to form tapes. Further self-assembly leads to the formation of fibrils, which in turn self-assemble to form fibers. The existence of these forms has been confirmed by nanoparticle marking. Thiol-protected gold nanoparticles (GNPs) have been used to probe the initial stages of the molecular organization of oligo(p-phenylenevinylene) (OPV) gelators. The hybrid materials prepared by the self-assembly of OPVs and GNPs are characterized by optical microscopy, fluorescence microscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. GNPs are located preferentially on the sides of the OPV structures, which implies the presence of alkyl chains at the edges, which makes the assemblies hydrophobic. TEM analyses at the early stages of self-assembly show tapes that have a width of 4 nm, which upon further self-assembly, form fibrils through hydrogen bonding. The experiment was performed with GNPs protected with dodecane and octadecane thiols. The existence of tapes, ribbons, fibrils, and fibers were confirmed by nanoparticle marking. Based on the experimental data, we have proposed a hierarchical model for the self-assembly of OPV molecules. The presence of nanoparticles does not alter the morphology or electronic properties of the OPV structures, as revealed by microscopic and spectroscopic studies.