Plasmonic Cyclic Au Nanosphere Hexamers

Customized Self-Assembled Gold Nanoparticle-DNA Origami Composite Templates for Shape-Directed Growth of Plasmonic Structures

The metal plasmonic nanostructure has the optical property of plasmon resonance, which holds great potential for development in nanophotonics, bioelectronics, and molecular detection. However, developing a general and straightforward method to prepare metal plasmonic nanostructures with a controllable size and morphology still poses a challenge. Herein, we proposed a synthesis strategy that utilized a customizable self-assembly template for shape-directed growth of metal structures. We employed gold nanoparticles (AuNPs) as connectors and DNA nanotubes as branches, customizing gold nanoparticle-DNA origami composite nanostructures with different branches by adjusting the assembly ratio between the connectors and branches. Subsequently, various morphologies of plasmonic metal nanostructures were created using this template shape guided strategy, which exhibited enhancement of surface-enhanced Raman scattering (SERS) signals. This strategy provides a new approach for synthesizing metallic nanostructures with multiple morphologies and opens up another possibility for the development of customizable metallic plasmonic structures with broader applications.

Chiroplasmonic DNA Scaffolded "Fusilli" Structures

DNA is an ideal template for the design of nanoarchitectures with molecular-like features. Here, we present an optimized assembly strategy for the concatenation of DNA quasi-rings into long scaffolds. Ionic strength, which played a major role during self-assembly, produced the expected high quality only at 15 mM MgCl2. Atomic force microscopy (AFM) characterization showed several micrometer long tubular structures that were used as templates for the positioning of plasmonic nanoparticles (NPs) along a three-dimensional helical path using DNA tethers. As imaged by high-resolution scanning transmission electron microscopy (HR-STEM) and modeled by theoretical calculations, the NPs distributed into a "fusilli" fashion (i.e., a helical pasta shape), displaying chiroptical activity as revealed by a bisignated CD absorption, centered at the plasmon resonance wavelength. The present structures contribute to enrich the ever-developing arena of chiroplasmonic DNA-based nanomaterials and demonstrate that large assemblies are attainable for their future application to develop metamaterials.

Branched Aluminum Nanocrystals with Internal Hot Spots: Synthesis and Single-Particle Surface-Enhanced Raman Scattering

Owing to their unique and sustainable surface plasmonic properties, Al nanocrystals have attracted increasing attention for plasmonic-enhanced applications, including single-particle surface-enhanced Raman scattering (SERS). However, whether Al nanocrystals can achieve single-particle SERS is still unknown, mainly due to the synthetic difficulty of Al nanocrystals with internal gaps. Herein, we report a regrowth method for the synthesis of Al nanohexapods with tunable and uniform internal gaps for single-particle SERS with an enhancement factor of up to 1.79 × 10⁸. The uniform branches of the Al nanohexapods can be systematically tuned regarding their dimensions, terminated facets, and internal gaps. The Al nanohexapods generate hot spots concentrated in the internal gaps due to the strong plasmonic coupling between the branches. A single-particle SERS measurement of Al nanohexapods shows strong Raman signals with maximum enhancement factors comparable to that of Au counterparts. The large enhancement factor indicates that Al nanohexapods are good candidates for single-particle SERS.