What is next in polymer-grafted plasmonic nanoparticles?

Abstract

Plasmonic metal nanoparticles have unique optical properties, such as localized surface plasmon resonance resulting from the oscillation of free electrons. Integrating discrete plasmonic nanoparticle into assembled nanostructures enables interparticle plasmon coupling and collective properties that are often absent in their discrete counterparts. Synthetic polymers as surface ligands on plasmonic nanoparticles can stabilize the nanoparticles, define the surface properties, control the interparticle interactions and therefore direct the nanoparticle self-assembly. Given the length scale of polymers comparable to the size of plasmonic nanoparticles of interest, polymer ligands are promising for precisely controlling the interparticle interaction. Engineering polymer ligands in the terms of their chemical composition, grafting density, anchoring groups and chain lengths is critical to control the assembly nanostructures and plasmon coupling of adjacent nanoparticles. The focus of this perspective is to identify and address the unmet challenges in the field of polymer-grafted plasmonic nanoparticles (PGNPs). Key unresolved issues broadly covered from the design of PGNP building blocks to their self-assembly are illustrated by highlighting a few examples. In views of more robust building blocks, the choice of inexpensive metals, the new anchoring groups and precision control of polymer ligands are discussed. We further consider the challenges in breaking the surface symmetry of plasmonic nanoparticles and designing synthetic polymers to achieve reversibility and directionality in the self-assembly of PGNPs.