Stability and Reversal of the Optical Activity in Chiral Wurtzite CdSe Nanocrystals

With the development of nanotechnology, it is found that the chiral semiconductor nanocrystals have vast potential applications in many different fields, such as biological labels, chiral analysis and detectors, enantioselective separation, gene editing, spin electronic devices, and so on. However, the study of their stability is rare. Here, we report the stability of chiral wurtzite CdSe quantum rods (QRs) and nanoplatelets (NPLs) with conventional chiral ligands of cysteine kept in an ambient atmosphere. The chiral QRs show specific stability in water solvents; however, that of the chiral NPLs is weak, with completely reverse chiroptical signs in just 90 min. The combination of experimental proofs and theoretical results reveals that the reversed optical activities come from the switch of electronic transition dipole moments of chiral CdSe surfaces. Our study helps to survey the construction of more stable chiral semiconductor nanomaterials, which is the key to improving their applications.