Template-assisted self-assembly of achiral plasmonic nanoparticles into chiral structures

The acquisition of strong chiroptical activity has revolutionized the field of plasmonics, granting access to novel light-matter interactions and revitalizing research on both the synthesis and application of nanostructures. Among the different mechanisms for the origin of chiroptical properties in colloidal plasmonic systems, the self-assembly of achiral nanoparticles into optically active materials offers a versatile route to control the structure-optical activity relationships of nanostructures, while simplifying the engineering of their chiral geometries. Such unconventional materials include helical structures with a precisely defined morphology, as well as large scale, deformable substrates that can leverage the potential of periodic patterns. Some promising templates with helical structural motifs like liquid crystal phases or confined block co-polymers still need efficient strategies to direct preferential handedness, whereas other templates such as silica nanohelices can be grown in an enantiomeric form. Both types of chiral structures are reviewed herein as platforms for chiral sensing: patterned substrates can readily incorporate analytes, while helical assemblies can form around structures of interest, like amyloid protein aggregates. Looking ahead, current knowledge and precedents point toward the incorporation of semiconductor emitters into plasmonic systems with chiral effects, which can lead to plasmonic-excitonic effects and the generation of circularly polarized photoluminescence.