Tunable Chiroptical Activity in Branched Ag@Au Nanoparticles with Molecular Chirality and Geometric Chirality.

Chiral plasmonic nanomaterials have attracted significant awareness due to their applications in chiral catalysis, biosensing, photonics, and separation. Constructing plasmonic core-shell nanomaterials with geometric chirality and desirable optical chirality is a crucial yet challenging task for extending the range of chiral plasmonic nanomaterials. Here, a two-step method is reported for the synthesis of Gold (Au) branches wrapped silver (Ag) nanocubes (L/DBAg@Au) with strong and tunable circular dichroism (CD) signals under the regulation of L/D-cysteine (L/D-Cys). The Au branches consisted of multiple pinwheel-like Au. Both experimental results and theoretical simulations have demonstrated that the CD signals of these structures originated from the synergism between molecular chirality and geometrical chirality. The CD signals in the visible region could be enhanced through coupling effects between Au and Ag. The CD signals and geometries evolved with the variations in Cys concentration, chiral molecule type, and incubation time. This work provides valuable insights to guide the rational design of plasmonic core-shell nanomaterials with geometric chirality.