Effects of different fatty acid ligands on the synthesis of CdSe nanocrystals

Abstract

We developed phosphine-free synthesis route for CdSe nanocrystals using oleic acid or stearic acid as ligands and liquid paraffin as the matrix. A new post process was used for Cd–stearic acid system to isolate the CdSe NCs preferably from the unreacted materials. All of the synthesis processes were performed in open air. We studied the effects of different fatty acid ligands on the crystal synthesis by the characterization of absorption and photoluminescence spectroscopy, powder X-ray diffraction, and transmission electron microscopy. The results show that compared to oleic acid ligands, the CdSe nanocrystals prepared by stearic acid ligands have narrower full width at half maximum (30–31 nm (stearic acid) versus 36–43 nm (oleic acid) at the growth temperature of 230 °C), higher photoluminescence quantum efficiency [10 % (stearic acid) versus no more than 5 % (oleic acid)], and crystallinity. This surfactant system was used to prepare size-tunable CdSe nanocrystals at lower growth temperatures (220–260 °C) and with better polydispersity relative to alternative schemes for zinc-blende crystal structures.