Amplification of Photochemical Chiroptical Activity of Chiral Gold Nanocubes

Abstract

Chiral plasmonic nanostructures enable exceptionally high dissymmetry factors (g-factors) compared to chiral molecules and present unparalleled opportunities in light manipulation, polarization-sensitive photochemistry, and chiral sensing. Here polarization-dependent plasmonic chemistry on chiral gold nanocubes (AuNCs) is presented, leveraging the high sensitivity of surface-enhanced Raman scattering (SERS). The AuNCs exhibit strong optical activity and localized surface plasmon resonances acting as highly efficient nanoscale light antennae. Employing the hot electron-induced dehalogenation of 8-Bromoadenine as a model reaction, it is demonstrated that circularly polarized light induces asymmetric reaction rates due to circular dichroism (CD) in hot electron generation efficiency. Astonishingly, the photochemical g-factor, quantified by the differential reaction rate coefficients under left-handed and right-handed circularly polarized light, surpasses its optical counterpart and can be further enhanced by laser intensity. Remarkably, multilayer assemblies of AuNCs exhibit a reversal in photochemical CD, which is tuneable via laser power and enables further g-factor enhancement. Comprehensive electromagnetic simulations of extinction spectra and hot electron generation maps corroborate the profound impact of particle arrangement on the optical g-factor and the g-factor for hot-electron generation. This work demonstrates a systematic approach to enhance the photochemical chiroptical response of chiral AuNCs, paving the way for extraordinary control over chemical reactions with light.