Gold Core‐DNA‐Silver Shell Nanoparticles with Intense Plasmonic Chiroptical Activities

Abstract

The strong plasmonic chiroptical activities of gold core‐DNA‐silver shell nanoparticles (NPs) are reported for the first time, using cytosine‐rich single‐stranded DNA as the template for the guidance of silver shell growth. The anisotropy factor of the optically active NPs at 420 nm reaches 1.93 × 10−2. Their chiroptical properties are likely induced by the DNA–plasmon interaction and markedly amplified by the strong electromagnetic coupling between the gold core and silver shell.

Core–Gap–Shell Nanoparticles@Polyaniline with Tunable Plasmonic Chiroptical Activities by pH and Electric Potential Dual Modulation

“…Importantly, these c-CGS Au NRs showed greatly enhanced chiral responses compared to the case before shell growth (Figure S5), and the intensity was almost unchanged after removal of the Cys molecules from the outer surface of the shell (Figure S6), suggesting that the enhancement effect arose from the natural electromagnetic field hotspots in the intragap. This has also been substantiated by the simulations of the proposed effective medium theory, which employed a similar model of chiral molecules being encapsulated in a nanocavity, with the origin of the chiral response attributed to the electromagnetic near-field enhancement. , The intensity and position of the chiral peak were more dependent on the molecular density, the number of hotspots, and the geometry of the plasmonics. − During shell growth, the low concentration (5 nM) of Cys molecules was unable to support a significant chiral response due to the less quantity of chiral sources and hotspots (Figure A–C,J top), while medium concentration (50 nM) was considered to have the opportunity to increase both of chiral sources and hotspot density while maintaining the simple rod shape (Figure D–F). On further increasing the concentration (500 nM), a large number of free strong ligands bonding immediately to freshly exposed crystal faces induced locally anisotropic growth and inhibited the formation of hotspots.…”

Enhancing the plasmonic circular dichroism by entrapping chiral molecules at the core–shell interface of rod-shaped Au@Ag nanocrystals

“…Two related reports demonstrated that spherical Au@Ag core-shell nanoparticles can also show quite large PCD signals. 32,33 These nanoparticles have different structures from ours. In the first report, DNA molecules were entrapped at the grain boundaries of the polycrystalline shell.…”

Interband Absorption Enhanced Optical Activity in Discrete Au@Ag Core–Shell Nanocuboids: Probing Extended Helical Conformation of Chemisorbed Cysteine Molecules

“…For instance, cysteine‐coated Ag nanospheres and nanorods show CD enhancements of 36 and 62 times (Figures S2 and S3) while cysteine‐coated Au nanorods and nanospheres exhibit no detectable CD signal (Figure S4). This is probably due to the fact that Ag is more susceptible to environmental changes than Au, and therefore structural changes of chiral molecules could occur more easily on Ag . Surprisingly, by comparing with the permittivity of Ag in Figure d, we find that the unusual CD band is located exactly at the interband absorption region of Ag (shadowed area, 220–320 nm).…”