Patchy metal nanoparticles with polymers: controllable growth and two-way self-assembly.

We report a new design of polymer-patched gold nanoparticles (AuNPs) with controllable interparticle interactions in terms of their direction and strength. Patchy AuNPs (pAuNPs) are prepared through hydrophobicity-driven surface dewetting under deficient ligand exchange conditions. Using the exposed surface on pAuNPs as seeds, a highly controllable growth of AuNPs is carried out via seed-mediated growth while retaining the size of polymer domains. As guided by ligands, these pAuNPs can self-assemble directionally in two ways along the exposed surface (head-to-head) or the polymer-patched surface of pAuNPs (tail-to-tail). Control of the surface asymmetry/coverage on pAuNPs provides an important tool in balancing interparticle interactions (attraction vs. repulsion) that further tunes assembled nanostructures as clusters and nanochains. The self-assembly pathway plays a key role in determining the interparticle distance and therefore plasmon coupling of pAuNPs. Our results demonstrate a new paradigm in the directional self-assembly of anisotropic building blocks for hierarchical nanomaterials with interesting optical properties.

Facile synthesis of water-dispersible poly(3-hexylthiophene) nanoparticles with high yield and excellent colloidal stability.

There has been growing interest in water-processable conjugated polymers for biocompatible devices. However, some broadly used conjugated polymers like poly(3-hexylthiophene) (P3HT) are hydrophobic and they cannot be processed in water. We herein report a facile yet highly efficient assembly method to prepare water-dispersible pyridine-containing P3HT (Py-P3HT) nanoparticles (NPs) with a high yield (>80%) and a fine size below 100 nm. It is based on the fast nanoprecipitation of Py-P3HT stabilized by hydrophilic poly(acrylic acid) (PAA). Py-P3HT can form spherical NPs at a concentration up to 0.2 mg/mL with a diameter of ∼75 nm at a very low concentration of PAA, e.g., 0.01-0.1 mg/mL, as surface ligands. Those negatively charged Py-P3HT NPs can bind with metal cations and further support the growth of noble metal NPs like Ag and Au. Our self-assembly methodology potentially opens new doors to process and directly use hydrophobic conjugated polymers in a much broader context.