Molecular chirality can be strongly influenced by plasmonic environments. Observing and distinguishing the physical and chemical origins at plasmon–molecule interfaces, especially at the single-molecule level, have remained a great challenge. Herein, through DNA-mediated sub-nanometer assembly, we achieved the first observation of plasmon-altered circular dichroism from single-molecule chiroplasmonic complexes. Experimental and theoretical results indicated that, under such sub-nanometer confinement, the chiroptical response is predominantly governed by the coupling between the plasmonic field gradient and the molecule’s extended electronic distribution. We devised a critical strategy contrasting the chiroptical response under DNA-controlled physical proximity with that induced by direct chemical binding using atomic-site modification as a probe. This comparison allowed us to differentiate the roles of electromagnetic effects from chemical interfacial interactions in reshaping molecular chirality. This work offers a generalizable framework for studying competing mechanisms at plasmon–molecule interfaces, paving the way for the advancement of chiral photonics and optoelectronics at the atomic scale.
Li et al. (Tue,) studied this question.