Group II-VI semiconductor nanoplatelets present narrow optical properties thanks to their thickness, which is the only confined direction, defined at the atomic scale without roughness. It makes them appealing for optoelectronic devices. Besides, in NPLs, the wide top and bottom facets are extended over 1000s of nm². Thus, these facets can be assimilated to substrates for the self-assembly of molecules. At the end of the syntheses, the carboxylate ligands induce a tensile in-plane stress. These pristine ligands can be exchanged with X-type ligands, which can be halide, thiolate, phosphonate or chiral ligands. And, depending on their anchoring groups, the in-plane stress can vary from a tensile to a compressive stress, inducing thus a distortion of the crystal structure.

Here, we will first show that in CdSe NPLs capped with in-plane compressive stress thiolate ligands, Cd²⁺ are effectively exchanged by Cu⁺ cations, thus enabling the synthesis of Cu_2-xSe NPLs with thicknesses comprise between 2 monolayers (MLs) and 5 MLs. Indeed, cation exchange is an interesting method to obtain nanoparticles which shape cannot be directly synthesized. In this case, the exchange most probably happens through the edges and its kinetic can be modified depending on the aliphatic chain length of the thiolate ligands. Such Cu_2-xSe NPLs can be used as template for further cation exchange with Hg²⁺, leading to the synthesis of HgSe NPLs. However, the process is tedious and requires 2 consecutive steps including one in the glovebox. So we have demonstrated that a cation exchange from Cd²⁺ to Hg²⁺ could be co-catalyzed with Ag⁺ cations. Through this method, HgCdSe NPLs are obtained and enable to overcome the limitation of the direct cation exchange from Cd²⁺ to Hg²⁺ to only two cationic planes. The obtained NPLs are now showing a variation of the optical properties with quantum confinement.

Finally, I will show that pristine ligands can be exchanged with chiral ligands, in the aim of circular dichroism optical properties. We are showing a direct ligand exchange in ethanol from carboxylate to tartrate ligands, inducing the self-assembly of the tartrate ligands in two different conformations exhibiting opposite circular dichroism signal. The emergence of the circular dichroism optical properties comes from a good coupling of the ligands on the surface and an orthorhombic crystal distorsion. The dissymmetric factor can reach values as high as 1.2% for extended NPLs.