A great challenge for nanotechnology is to controllably organize anisotropic nanomaterials into well-defined three-dimensional superstructures with customized properties. Here we successfully constructed anisotropic Au nanorod (AuNR) helical superstructures (helices) with tailored chirality in a programmable manner. By designing the 'X' pattern of the arrangement of DNA capturing strands (15nt) on both sides of a two-dimensional DNA origami template, AuNRs functionalized with the complementary DNA sequences were positioned on the origami and were assembled into AuNR helices with the origami intercalated between neighboring AuNRs. Left-handed (LH) and right-handed (RH) AuNR helices were conveniently accomplished by solely tuning the mirrored-symmetric 'X' patterns of capturing strands on the origami. The inter-rod distance was precisely defined as 14 nm and inter-rod angle as 45°, thus a full helix contains 9 AuNRs with its length up to about 220 nm. By changing the AuNR/origami molar ratio in the assembly system, the average number of AuNR in the helices was tuned from 2 to 4 and 9. Intense chiroptical activities arose from the longest AuNR helices with a maximum anisotropy factor of ∼0.02, which is highly comparable to the reported macroscopic AuNR assemblies. We expect that our strategy of origami templated assembly of anisotropic chiral superstructures would inspire the bottom-up fabrication of optically active nanostructures and shed light on a variety of applications, such as chiral fluids, chiral signal amplification, and fluorescence combined chiral spectroscopy.

Discrete three-dimensional (3D) plasmonic nanoarchitectures with well-defined spatial configuration and geometry have aroused increasing interest, as new optical properties may originate from plasmon resonance coupling within the nanoarchitectures. Although spherical building blocks have been successfully employed in constructing 3D plasmonic nanoarchitectures because their isotropic nature facilitates unoriented localization, it still remains challenging to assemble anisotropic building blocks into discrete and rationally tailored 3D plasmonic nanoarchitectures. Here we report the first example of discrete 3D anisotropic gold nanorod (AuNR) dimer nanoarchitectures formed using bifacial DNA origami as a template, in which the 3D spatial configuration is precisely tuned by rationally shifting the location of AuNRs on the origami template. A distinct plasmonic chiral response was experimentally observed from the discrete 3D AuNR dimer nanoarchitectures and appeared in a spatial-configuration-dependent manner. This study represents great progress in the fabrication of 3D plasmonic nanoarchitectures with tailored optical chirality.

The ability to dynamically tune the self-assembled structures of nanoparticles is of significant interest in the fields of chemistry and material studies. However, it continues to be challenging to dynamically tune the chiral superstructures of nanoparticles and actively switch the chiral optical properties thereof. Here, we dynamically controlled a gold nanorod 3D chiral plasmonic superstructure (a stair helix with a pinwheel end view) templated by a DNA origami supramolecular polymer, using DNA-toehold-mediated conformational change in the DNA template. The gold nanorod chiral plasmonic helix was controllably reconfigured between a tightly folded state (with a small inter-rod angle) and an extended state (with a wide inter-rod angle) of the same handedness, or between two mirror-image-like structures of opposite handedness. As a result, the chiral plasmonic properties of the gold nanorod helix superstructures, in terms of the circular dichroism amplitude, peak response frequency, and signature of chirality, were actively switched upon the DNA-guided structural reconfiguration. We envision that the strategy demonstrated here will boost the advancement of reconfigurable chiral materials with increased complexity for active light control applications through rational molecular design and predictable self-assembly procedures.