Investigating the surface ligand dynamics of colloidal semiconductor nanocrystals

by Ong, Grace L.; Peng, Xiaogang

The colloidal II-VI semiconductor nanocrystals system of CdSe is used as the model for a quant. study of ligand dynamics. CdSe nanocrystals are commonly synthesized with alkylamines as the surface ligands. However, the existence of these original ligands during surface ligand studies biased the results. Here, we introduce an optimized quant. method of removing the original ligands and replacing them with more labile ligands, such as pyridine. Pyridine is a very labile ligand for CdSe nanocrystals, providing essentially "naked" nanocrystals for various surface ligand manipulations such as alkylamine ligand adsorption and desorption with different concns., chain lengths, and temps. With the aid of in-situ time-resolved photoluminescence, UV-Vis absorbance, and NMR spectroscopy, the ligand dynamics is investigated. A theor. and math. model of the system is proposed, and exptl. data is fit using the designated math. method to obtain important kinetics and thermodn. consts. of the system.