Amplification of photochemical chiroptical activity of chiral gold nanocubes

Chiral plasmonics has garnered profound potential in light manipulation, polarization-sensitive photochemistry and chiral sensing due to the dissymmetry factors (g-factors) exceeding significantly the ones of chiral molecules. We have investigated polarization-dependent plasmonic chemistry on chiral gold nanocubes (AuNC) through surface-enhanced Raman scattering (SERS). The AuNC exhibit substantial optical activity and a pronounced localized surface plasmon resonance. The hot electron induced dehalogenation of 8-Bromoadenine, adsorbed on chiral AuNC, has been employed as a model reaction to understand the effect of polarized light on plasmon-induced chemical reactions. Our observations reveal a circular dichroism (CD) of the hot electron generation efficiency resulting in asymmetric reaction rates. The photochemical g-factor, determined by the differential reaction rate coefficients with left-handed and right-handed circularly polarized light, surpasses the optical g-factor by a factor of 2. Moreover, a reversal of photochemical CD is observed on multilayer coverage of particles, which is laser power dependent and allows for a further amplification of g-factor just by increasing the light intensity. Calculations of extinction spectra and hot electron generation maps with different polarization incident on the chiral AuNC confirm a significant influence of the arrangement of particles on the g-factor. This work opens a new domain in asymmetric photocatalysis.