Dr. Jonathan Faiz, Senior Associate Editor for Angewandte Chemie, talks to Professor Eugenia Kumacheva, University of Toronto, Canada, about her article that has recently been accepted for publication in Angewandte Chemie.

You have explored the assembly of metal nanoparticles. What was the inspiration behind this study?

Several years ago, we were inspired by the remarkable similarity between molecular polymerization reactions and the one-dimensional self-assembly of metal nanoparticles. This similarity, which spans two orders of magnitude in length scales, inspired us to conceptualize and design hetero-nanostructures by mimicking molecular copolymerization reactions. Importantly, from the very beginning we undertook a quantitative approach to nanoparticle co-assembly.

Plasmonic nanostructures seem to be a popular theme at the moment. What is it about your research that is particularly significant?

By providing “molecular” guidance for the generation of one-dimensional plasmonic heterostructures, our work can contribute in identifying the most efficient types of plasmonic nanostructures and may assist in discovery of new plasmonic properties. For example, it can be used for the fundamental studies of Fano plasmon modes.

Why was your attention focused on these types of materials?

Our group has a strong interest in plasmonics. We focused on the self-assembly of chains of plasmonic nanoparticles, because they show interesting optical properties, e.g., extinction and surface enhanced Raman scattering. However the approach to nanoparticle copolymerization described in our paper is not limited to plasmonic nanoparticles, and it can be used for hetero-assembly of a broad range of nanoparticles, including quantum dots and magnetic nanoparticles.

What is the broader impact of this paper for the scientific community?

We have shown that in the course of self-assembly, nanoparticles act as artificial co-monomer molecules. This analogy offers the ability to create a model system and test many assumptions made in molecular copolymerization. Note that copolymerization of nanoparticles can be studied by a set of tools that are not available for molecular copolymerization, e.g., by direct visualization of colloidal copolymers or by monitoring plasmonic coupling between individual nanoparticles. On the other hand, copolymers of nanoparticles show interesting coupled optical, electronic, and magnetic properties, which depend on the nanochain structure. Our “molecular copolymerization” approach offers control over the structure and properties of nanoparticle assemblies.

How will you follow up on this discovery?

We are interested in exploring copolymerization of a broad range of nanoparticles with different compositions, sizes, and shapes. Single-particle spectroscopy experiments conducted in collaboration with Prof. Stephan Link will be used to analyze the structure−property relationship for such assemblies. We plan to enhance the optical properties of the nanochains by achieving greater nanoparticle co-linearity and increasing the area of contact between them. Other polymerization strategies will be used to co-assemble of different types of nanostructures, beyond 1D ensembles.

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The article they talked about:

• Copolymerization of Metal Nanoparticles: A Route to Colloidal Plasmonic Copolymers,
  Kun Liu, Ariella Lukach, Kota Sugikawa, Siyon Chung, Jemma Vickery, Heloise Therien-Aubin, Bai Yang, Michael Rubinstein, Eugenia Kumacheva,
  Angew. Chem. Int. Ed. 2014.
  DOI: 10.1002/anie.201309718