Fabricating Chiral Films of Cesium Lead Halide Perovskite Nanocrystals
Quantum dots (QDs) are nanocrystals small enough to confine excitons, which gives them photoluminescent properties and a wide variety of applications. QDs can display chiral properties if they are bound with chiral surface ligand molecules. Chiral QDs have applications in enantioselective synthesis, biosensing, and as circularly polarized light emitters. For many applications, it is useful to have the QDs in a tightly-packed film rather than in solution. In this work, I performed post-synthetic ligand exchange on Lead Halide Perovskite (LHP) QDs using both solid-state and solution-state reactions with various candidate ligands, including N-benzylcinchonidinium chloride and 2-aminobutyric acid. In addition, I performed a direct synthesis of LHP QDs bound with chiral sulfonic acid ligands based on a modification of published procedures. I created films of exchanged QDs by spin-coating, and characterized the resulting solutions and films by UV-Vis absorption, photoluminescence (PL) spectroscopy, and time-resolved PL. I used Fourier-Transform Infrared spectroscopy to determine the presence of exchanged ligands. Finally, I examined the chiral properties of the QD solutions and films using circular dichroism spectroscopy, which measures differential absorption of left and right circularly polarized light. These results will serve as a starting point for future synthesis of chiral LHP QDs and research into their applications.