Magnetic Plasmon Networks Programmed by Molecular Self-Assembly

Nanoscale manipulation of magnetic fields has been a long-term pursuit in plasmonics and metamaterials, as it can enable a range of appealing optical properties, such as high-sensitivity circular dichroism, directional scattering, and low-refractive-index materials. Inspired by the natural magnetism of aromatic molecules, the cyclic ring cluster of plasmonic nanoparticles (NPs) has been suggested as a promising architecture with induced unnatural magnetism, especially at visible frequencies. However, it remains challenging to assemble plasmonic NPs into complex networks exhibiting strong visible magnetism. Here, a DNA-origami-based strategy is introduced to realize molecular self-assembly of NPs forming complex magnetic architectures, exhibiting emergent properties including anti-ferromagnetism, purely magnetic-based Fano resonances, and magnetic surface plasmon polaritons. The basic building block, a gold NP (AuNP) ring consisting of six AuNP seeds, is arranged on a DNA origami frame with nanometer precision. The subsequent hierarchical assembly of the AuNP rings leads to the formation of higher-order networks of clusters and polymeric chains. Strong emergent plasmonic properties are induced by in situ growth of silver upon the AuNP seeds. This work may facilitate the development of a tunable and scalable DNA-based strategy for the assembly of optical magnetic circuitry, as well as plasmonic metamaterials with high fidelity.