Biomolecules-Templated Plasmonic Supramolecular Assembly and Emergent Chiroptical Behaviors

Biomolecules such as proteins and DNA receive extensive attention due to their potentials to guide hierarchical materials assembly with emergent properties and behaviors that are otherwise difficult to realize without their involvement. Herein we demonstrate the integration of fibrous proteins or cubic DNA origamis with plasmonic gold nanoparticles towards designing hybrid chiroptically active materials. Through modifying cysteine molecules at selective sequences of protein subunits or introducing thiol groups to the DNA sequences, these biomolecular templates are bestowed with high binding affinity to gold nanoparticles, supporting effective gold attachment and anchoring. Low-symmetry assembly of plasmonic gold nanoparticles translates to promising optical asymmetry, shown by both simulated and experimental circular dichroism (CD) patterns. Additionally, we built a dark-field scattering microscopy equipped with circular polarization that grant us the capability to detect CD patterns at single particle level. Made possible by the versatility of biomolecular templates, controllability of assembly approaches, and single-particle level CD measurement, we study the structure-property relationship and effectively pinpoint structural dependence of CD such as particle sizes, orientations, and plasmonic coupling. This work provides insights into hierarchical assembly templated by biomolecules and their emergent chiroptical properties with energy harvesting and molecular detection implications.