Helicoid plasmonic nanoparticles with intrinsic chirality are an emerging class of artificial chiral materials with tailorable properties. The ability to extend their chiroplasmonic responses to the near-infrared (NIR) range is critically important for biomedical and nanophotonic applications, yet the rational design of such materials remains challenging.

Recently, Wenxin Niu's research team of Changchun Institute of Applied Chemistry published an article in Nature Communications. In this study, a strategy employing chiral plasmon-dielectric coupling is proposed to manipulate the chiroptical responses into the NIR region with high optical anisotropy. Through this strategy, the helicoid Au@Cu₂O nanoparticles with structural chirality are designed and synthesized with tunable and enriched NIR chiroptical responses. Specially, a high optical anisotropy (g-factor) with a value of 0.35 is achieved in the NIR region, and multi-band chiroptical behaviors are observed. Spectral and electromagnetic simulations elucidate that strong coupling between chiroplasmonic core and chiral dielectric shell with high refractive index contributes to the rich and strong chiroptical responses, which are related to the interplay between various emerged and enhanced electric and magnetic multipolar resonance modes proved by multipole expansion analysis. Moreover, the helicoid Au@Cu₂O nanoparticles display greater polarization rotation capability than the helicoid Au nanoparticles. This work offers mechanistic insights into chiral plasmon-dielectric coupling and suggests a general approach of creating NIR chiroplasmonic materials.

Xiali Lv①, Yu Tian①, Fengxia Wu, Xiaoxi Luan, Fenghua Li, Zhili Shen, Guobao Xu, Kun Liu, Wenxin Niu*, Nature Communications 2024, 15, 9234.

https://doi.org/10.1038/s41467-024-53705-4

The strong coupling between helicoid Au core and helicoid Cu₂O shell with high refractive index leads to the richer and stronger chiroptical responses than single helicoid Au core.