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Ligand-exchange reactions of wurtzite CdSe quantum platelets (QPs) and quantum belts (QBs) with methyl viologen (MV2+) and the derivative ligands MV2+(CH2)nNH2 (n = 2, 4, or 6) are investigated. The QP and QB photoluminescence is quenched after partial ligand exchange. Spectroscopic and compositional data establish that this initial ligand substitution occurs on the thin QP and QB edges. The MV2+(CH2)nNH2 ligands are shown to be more-efficient photoluminescence quenchers than the parent MV2+ ion. The ligands on the thin, nonpolar, long-edge facets quench the photoluminescence via the trapping of excitons. Transient absorption experiments indicate the excitons dissociate, and electron transfer to the MV2+(CH2)nNH2 ligands only occurs at the polar, short-edge facets of the wurtzite CdSe QPs and QBs. Electron transfer to the MV2+(CH2)nNH2 ligands occurs within 100 fs when exciting at the band edge and on longer time scales, due to intraband relaxation, when exciting at higher energies. 

Wurtzite CdSe quantum belts with L-type n-octylamine, L-type ammonia, or Z-type Cd(oleate)2 ligands are exchanged for several metal-dithiocarbamate ligands [M(S2CNR1R2)2]: Cd(S2CNPhMe)2, Cd(S2CNEt2)2, Zn(S2CNPhMe)2, and Zn(S2CNEt2)2. Successful ligand exchange with all M(S2CNR1R2)2 compounds occurs from {CdSe[Cd(oleate)2]0.19} quantum belts (QBs), which induce similar spectral shifts in the absorption spectra of the ligand-exchanged QBs. Spectroscopic data, experimentally determined lattice strains, and ligand exchanges with [Na][Et2NCS2] and [NH4][MePhNCS2] establish that the [M(S2CNR1R2)2] ligands bind as bound-ion-paired X-type ligands with (S2CNR1R2)− groups ligated directly to the QB surfaces and [M(S2CNR1R2)]+ groups serving as the charge-balancing ion-paired countercations. The X-type dithiocarbamate ligands do not impart any special electronic effects to the CdSe QBs.