Chiral Molecule-Embedded Au@Ag Core–Shell Decahedrons with Enhanced Circular Dichroism

Chiral plasmonic nanostructures provide an effective way to enhance circular dichroism (CD) activities of natural chiral molecules due to the strong coupling effect between molecular chirality and the surface plasmon. Nonetheless, the impact of the nanostructure parameters on the CD enhancement and the origin of the CD response is still not well-investigated. Here, we report a seed-mediated growth method to synthesize discrete Au@Ag core-shell decahedrons in the presence of cysteine by using concave 5-fold twinned Au nanocrystals as seeds. The produced core-shell decahedrons display a strong CD response in the plasmon resonance region, and the maximum Kuhn's dissymmetry value (g factor) can reach to as high as 5.8 × 10^-3 as well as a large CD enhancement factor over 2000. Comprehensive experiments reveal that embedded chiral cysteine in the outmost layer of the Ag shell plays the paramount role in inducing the CD activity, which ensures the good stability of the CD response of the nanostructures under long-term storage. Our finding inspires the rational design and synthesis of plasmonic CD systems with strong enhancement of the CD activities and expands their potential applications in chiral signal amplification and biosensing.