Structure-Modulated Circular Dichroism in Chiral Plasmonic Nanoparticles

Plasmonic nanoparticles with an intrinsic chiral structure have emerged as pivotal platforms for exploring advanced chiroptical phenomena, with promising applications in asymmetric catalysis, chirality sensing, biomedicine, and spin optoelectronics. Distinct from organic chiral molecules, chiral plasmonic nanoparticles exhibit strong and tunable circular dichroism responses originating from structure-dependent localized surface plasmon resonance. Therefore, the structure of chiral plasmonic nanoparticles, including size, geometry, anisotropy, and twinned structure, serves as the core determinant of their chiroptical performance, such as spectral line shape and dissymmetry factor. However, quantitative insights into the correlation between particle structure and chiroptical activities are increasingly important yet present substantial challenges. In this Account, we systematically elaborate on our recent efforts in establishing the fundamental principles of structure-dependent circular dichroism of chiral plasmonic nanoparticles and their emerging applications in spin electrocatalysis, chirality recognition, and circularly polarized luminescence. First, we introduce our recent advances in the controlled synthesis of single-crystalline chiral plasmonic nanoparticles through a seed-mediated chiral growth method. Through a few cases, including bichiral geometry, concave vortex cube, and sub-100 nm chiral nanoparticles, we clarify the underlying physical mechanism of structure-modulated circular dichroism in chiral plasmonic nanoparticles. For instance, we proposed the bichiral centers in chiral Au nanoparticles, where the competition between 4-fold and 3-fold chiral propellers leads to a tunable reversal of circular dichroism signals without inverting the overall geometric handedness. Second, we highlight our success in the integration of high-order symmetry with chiral geometry on individual twinned nanoparticles with increasing architectural diversity. Notably, starting with multitwinned (decahedral and icosahedral) seeds, we unlocked new classes of chiral plasmonic nanoparticles with 52 and 532 rotational symmetries, such as chiral pentagonal nanostars, pentagonal nanoprisms, and stellated nanoicosahedrons. These works demonstrated how twin boundaries and intrinsic lattice strain affect the evolution of geometric chirality as well as their optical chirality. Third, we showcase emerging applications of such chiral plasmonic nanoparticles in (i) tuning oxygen electrocatalysis through the chiral-induced spin selectivity effect, (ii) enantioselective recognition through chiral surface-enhanced Raman scattering, and (iii) amplification of circularly polarized luminescence through chiral plasmonic nanocavities. Finally, we outline future directions and challenges of chiral plasmonic nanoparticles with structure-modulated circular dichroism. It is envisioned that the controllable synthesis of chiral plasmonic nanomaterials with desired chiroptical activities not only sheds light on the underlying mechanisms dictating the intriguing chirality transfer from chiral molecules to chiral nanoparticles but also provides a coherent framework for rational design of chiral nanomaterials toward specific chirality-dependent applications.