Reversible Supracolloidal Self-Assembly of Cobalt Nanoparticles to Hollow Capsids and Their Superstructures

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The synthesis and spontaneous, reversible supracolloidal hydrogen bond-driven self-assembly of cobalt nanoparticles (CoNPs) into hollow shell-like capsids and their directed assembly to higher order superstructures is presented. CoNPs and capsids form in one step upon mixing dicobalt octacarbonyl (Co2CO8) and p-aminobenzoic acid (pABA) in 1,2-dichlorobenzene using heating-up synthesis without additional catalysts or stabilizers. This leads to pABA capped CoNPs (core ca. 5nm) with a narrow size distribution. They spontaneously assemble into tunable spherical capsids (d≈50-200nm) with a few-layered shells, as driven by inter-nanoparticle hydrogen bonds thus warranting supracolloidal self-assembly. The capsids can be reversibly disassembled and reassembled by controlling the hydrogen bonds upon heating or solvent exchanges. The superparamagnetic nature of CoNPs allows magnetic-field-directed self-assembly of capsids to capsid chains due to an interplay of induced dipoles and inter-capsid hydrogen bonds. Finally, self-assembly on air-water interface furnishes lightweight colloidal framework films.

Original languageEnglish
Pages (from-to)6473–6477
JournalAngewandte Chemie
Issue number23
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed


  • Capsids
  • Colloidal self-assembly
  • Electron tomography
  • Hydrogen bonding
  • Magnetic nanoparticles


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