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

The emerging concept of tunable plasmonic chirality is mostly observed as a reconfigurable behavior or a feature of complex chiral plasmonic assemblies. For discrete colloidal particles, it is challenging to achieve reversible tunability or a transient response with regard to chiroptical activities, particularly in the visible or near-infrared region. Herein, we demonstrate a stimulus-responsive system based on chiral molecule–achiral plasmonic nanoparticles coated with polyaniline (PANI) as a variable dielectric layer, in which l-/d-cysteine molecules are introduced between the gold core and the shell as a static chiral source, allowing the chiral transfer effect to be greatly amplified by the hotspot gap of sub-monomolecular thickness. By taking advantage of the responsive properties to either pH or the electric potential dual stimuli of PANI, which also provides a stable and real-time switchable dielectric environment for the whole system, dynamic tuning of the plasmon and its induced chiroptical activities of core–gap–shell nanoparticles@PANI were precisely obtained. This well-defined design provides an open platform for flexible and rational tailoring of plasmonic cores, chiral molecules, and variable dielectrics to chiroptical needs, which is important for realizing applications in chemical sensing, chiral nanocatalysis, enantioselective separations, and novel optical devices.