The assembly of nano-objects is a fundamental step toward the development of functional nanodevices. For the optimization of properties and functions, it is important to achieve structural precision.

Hongyu Chen and colleagues, Nanyang Technological University, Singapore, report the use of polymer shells to assist the 1D assembly of colloidal Au nanoparicles (NPs). The system is unique in that the aggregation of NPs follows a mode that is similar to chain-growth polymerization. This mode was essential for achieving high selectivity in the assembly of chains, thus reducing branching and other errors. Single-line chains of 300 NPs in length and double-line chains of 200 NPs were obtained.

The monomers that are used are AuNPs encapsulated by polystyrene-block-poly(acrylic acid) (AuNP@PSPAA). Induced by the structural transformation of the polymer micelles from spheres to cylinders, the embedded AuNPs are forced to form chains. Evidence is provided that the end-on aggregation (1-to-n coupling) is more favorable than the monomer aggregation (1-to-1 coupling).

These ultralong chains, with uniform width and interpartical spacing, could be potentially useful as plasmonic waveguide and device component.

• Unconventional Chain-Growth Mode in the Assembly of Colloidal Gold Nanoparticles,
  Hong Wang, Liyong Chen, Xiaoshuang Shen, Liangfang Zhu, Jiating He, Hongyu Chen,
  Angew. Chem. Int. Ed. 2012, 51.
  DOI: 10.1002/anie.201203088