Two-Phase Ligand Exchanges on CdSe Nanoplatelets

Ligand exchanges of L-type amine-ligated wurtzite CdSe nanoplatelets (NPLs) are investigated under two-phase conditions employing hexane as the nonpolar phase and DMF as the polar phase. Exchange with Z-type CdX2 (X = Cl, Br, and I) produces NPLs having the stoichiometries {CdSe[CdCl2](0.27)}, {CdSe[CdBr2](0.24)}, and {CdSe-[CdI2](0.26)} and results in the transfer of the NPLs from the top, nonpolar phase to the bottom, polar phase. Exchange with [NH4]X (X = Cl, Br, and I) results in L- to L'-type ligand exchange to ammonia (NH3) ligation. This exchange also results from the use of gaseous or aqueous ammonia. The CdX2 - and NH3 -ligated NPLs exhibit excellent dispersibility in DMF. The two-phase exchanges produce significantly different outcomes than comparable exchanges conducted under single-phase (toluene/methanol) conditions, showing that ligation stoichiometries, the identities of the ligands, and the dispersibilities of the ligand-exchanged NPLs are strongly influenced by the exchange conditions.