Investigation on the Nonlinear Chiroptical Activity of Cysteine Capped Ag₂₀ Nanoclusters

Exploring chiral phenomena on nanoscale level by capping organic ligand on the surface of metal nanoclusters has drawn increased attention in both theoretical and experimental aspects. Here, we perform a systematical theoretical investigation on the linear and nonlinear chiroptical properties of chiral ligand capped Ag20 nanoclusters. The influences of chiral ligand (D-cysteine) and structural configuration (V- and S-type connections) of Ag20 nanoclusters on the chiroptical behaviors of their complexes are investigated. The calculated results demonstrate that the electronic circular dichroism (ECD) and two-photon absorption (TPA) spectra of complexes are sensitive to their structural configuration. It is found that S-type connection will result in stronger ECD and two-photon circular dichroism (TPCD). And, the V-type connection will result in stronger TPA spectra. Additionally, based on analysis of the frontier molecular orbitals, it is confirmed that the hybridization between HOMOs plays a pivotal role in the induced chirality.