Highly distinctive MCD responses in thin palladium two-dimensional nanosheets: Effect of the in-plane quadrupolar resonance

We focus on magnetic circular dichroism (MCD) of thin palladium (Pd) nanosheets with different morphology or composition. Solid Pd nanosheets, synthesized by the CO-assisted reduction of Pd precursors, exhibit a single broad optical absorption peak in the near-IR range stemming from the dipolar plasmonic resonance. However, the MCD responses are counterintuitive and do not agree with those of the dipolar mode; we then find that they are associated with the in-plane quadrupolar resonance. We also examine MCD of hollow Pd and solid Pd Ag bimetallic nanosheets, and unlike the optical absorption, morphological and compositional modifications significantly modulate the MCD signatures.