INVESTIGATION OF THE SURFACE-MORPHOLOGY OF CAPPED CDSE NANOCRYSTALLITES BY P-31 NUCLEAR-MAGNETIC-RESONANCE

Room temperature P-31 magic angle sample spinning (MAS) nuclear magnet ic resonance (NMR) is used to study the phosphine chalconide species c oordinating the surface of CdSe nanocrystallites. Two surface species are identified: trioctylphosphine oxide (TOPO) and trioctylphosphine s elenide (TOPSe). The TOPO coordinates Cd surface sites while trioctylp hosphine (TOP) coordinates Se to produce surface TOPSe species. Chemic al removal of TOPSe linkages produces CdSe nanocrystallites passivated exclusively with TOPO. A double resonance experiment (P-31 and Se-77) characterizes the TOPSe species. Quantitative studies indicate coordi nation to nearly all surface Cd atoms and allows the development of a model for the morphology of an average crystallite surface.