Imprinting Chirality onto the Electronic States of Colloidal Perovskite Nanoplatelets

The direct synthesis of chiroptical organic-inorganic methylammonium lead bromide perovskite nanoplatelets that are passivated by R- or S-phenylethylammonium ligands is reported. The circular dichroism spectra can be divided into two components: (1) a region associated with a charge transfer transition between the ligand and the nanoplatelet, 300-350 nm, and (2) a region corresponding to the excitonic absorption maximum of the perovskite, 400-450 nm. The temperature- and concentration-dependent circular dichroism spectra indicate that the chiro-optical response arises from chiral imprinting by the ligand on the electronic states of the quantum-confined perovskite rather than chiral ligand-induced stereoselective aggregation.