Induced chirality in micron wave through electromagnetic coupling between chiral molecules and graphene nanostructures

The intricate mechanisms of plasmon-induced circular dichroism (CD) in a visible region are considered based on chemical and physical influences, in which a simple model and formulations are required. Here, we demonstrate theoretically that plasmon-induced CD is approximately contributed by the cross-interaction between equivalent electric and magnetic dipole moments for chiral molecules and plasmon nanostructures. To prove electromagnetic couplings, we introduce graphene into plasmon nanostructures and design asymmetrically inscribed graphene dual-rings arrays (IGDAs) with high-order hybrid modes. Results show that ultrahigh-order plasmon-induced CD signals are achieved in micron wave, which is easily detected by mature microwave technology. The maximum enhancement factor of induced CD could reach up to four orders of magnitude. In addition, an induced CD signal could be tuned only by varying the Fermi energy of IGDAs rather than by varying geometric dimensions. For different molecules, the electromagnetic couplings still hold. The results could be used to dynamically design chiral sensors in biology and chemistry.

Graphical abstractThe electromagnetic coupling model of plasmon-induced circular dichroism (CD) is proposed. Asymmetrically inscribed graphene dual-rings arrays are used to induce molecular CD signals in micron wave and form ultrahigh-order plasmon-induced CD signals, which could be tuned only by varying the Fermi energy of graphene. The maximum enhancement factor of induced CD could reach up to four orders of magnitude.Download high-res image (301KB)Download full-size image