Chenguang Ji


Date of Award

Spring 5-15-2023

Author's School

Graduate School of Arts and Sciences

Author's Department


Degree Name

Doctor of Philosophy (PhD)

Degree Type



This dissertation presents two-phase ligand exchanges on CdSe NPLs, and the applications of two-phase ligand exchanges to achieve interchange between L-type, Z-type and bound-ion-pair X type ligation on wurtzite CdSe NPLs. Post-synthetic ligand exchange is an important emerging method for optimizing the physical, catalytic, and spectroscopic properties of semiconductor nanocrystals. However, ligand exchanges conducted with small, polar, or charged ligands produce nanocrystals that are not dispersible in nonpolar liquids. Two-phase ligand exchange with immiscible polar and nonpolar liquids allows transfer of the nanocrystals from the nonpolar to the polar phase upon ligand exchange, in which stable nanocrystal dispersions are formed. First, by comparing two-phase ligand exchanges with single-phase ligand exchanges, we show that the exchange conditions employed strongly influence ligation stoichiometries, the identities of the bound ligands, and the dispersibility of the ligand-exchanged NPLs. We also report NH3 as a new ligand for wurtzite CdSe NPLs. Second, we demonstrate that halometallates of general formula XnMz– bind to wurtzite CdSe NPLs as intact, Z-type ligands through their Lewis-acidic metal centers. We discover that the polar-solvent molecule N-methylformamide (NMF) is an effective L-type ligand for wurtzite CdSe NPLs, and that NMF-ligated NPLs serve as useful synthetic intermediates, which is most likely to be synthetically useful in nanocrystals expressing nonpolar facets. Finally, we explore ligand exchanges and cation exchanges of wurtzite CdSe NPLs with Pb(II) ligands. The reactions of NMF-ligated NPLs with Pb(II) ligands (PbCl2, CsPbCl3 and CH3PbCl3) produce ligand-exchanged products at low Pb(II)/CdSe ratio, while cation exchanges happened at high Pb(II)/CdSe ratio. PbCl2 is determined to be a good ligand exchange reagent as it has the lowest reactivity in terms of ion exchange. By using a low Pb(II)/CdSe ratio, we can prepare PbCl2-ligated CdSe NPLs employing NMF-ligated CdSe NPLs as synthetic intermediate under single-phase conditions.


English (en)

Chair and Committee

William E. Buhro

Committee Members

Loomis A. Richard, Bryce Sadtler, Robert Wexler, Young-Shin Jun,

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