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Keywords:

  • Nanoparticles;
  • Self-assembly

Abstract

Isooctane dispersions of discrete isometric BaCrO4 nanoparticles or self-assembled linear chains of prismatic BaCrO4 nanoparticles were added as surfactant-coated seed crystals/nanostructures to Na2CrO4/NaAOT/Ba(AOT)2/isooctane microemulsion reaction solutions prepared at w = 10 with molar ratios favoring the de novo synthesis of either nanoparticle chains ([Ba2+]/ [CrO42–] = 1:1) or isolated nanoparticles ([Ba2+]/[CrO42–] = 1:5.5). Addition of BaCrO4 nanoparticles or chains under particle- or chain-producing conditions, respectively, resulted in preferential growth of the seeds with retention of particle morphology and nanostructure architecture. In contrast, addition of linear chains to microemulsion reaction solutions under particle-producing conditions resulted in disruption of the seed nanostructure and overgrowth of the released prismatic nanoparticles to produce discrete oval-shaped or cuboidal nanocrystals depending on the seed concentration used. Discrete faceted nanoparticles were also produced by seed-assisted synthesis when isometric nanoparticles were added at relatively high concentrations to chain-producing microemulsion reaction solutions; however, decreasing the seed population resulted in intact self-assembled linear chains and superlattices that consisted of interlinked prismatic nanoparticles with end-capped pseudo-hexagonal morphology. Growth of the seeds and their assembly/disassembly was consistent with a model of coupled synthesis and self-organization based on the strength of electrostatic interactions at the surfactant-crystal interface. The results suggest that microemulsion-based processes could be of general importance for controlling the secondary growth of pre-organized nanoparticle-based superstructures, as well as the morphological refinement of their constituent building blocks.