TOPO-capped CdSe nanocrystals with different sizes were synthesized by a slightly modified Peng and Pengs method, and pyridine-capped CdSe nanocrystals were obtained from TOPO-capped CdSe by exchange of TOPO with pyridine. By applying X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, photoluminescence (PL) and time-resolved PL (TRPL) spectroscopy, structural and optical characteristics of TOPO-capped and pyridine-capped CdSe are studied in detail. Analysis results show that, by exchanging the surface ligand from TOPO to pyridine, the crystalline quality and optical properties of CdSe nanocrystals are improved. During surface ligand exchange, the diameter of CdSe is decreased, which is caused by the loss of surface Cd and Se atoms with leaving TOPO molecules. The TRPL results suggest that the localized optical transitions of pyridine-capped CdSe, which result from defects and impurities existing in the nanocrystals, are suppressed, compared with those from the original TOPO-capped CdSe. The PL blue-shifts of pyridine-capped CdSe are also observed, and the PL and XPS results indicate that, when TOPO is substituted by pyridine, the surface electronic density of CdSe is re-distributed.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Inorganic Chemistry
- Materials Chemistry