Synthesis of non-spherical CdSe nanocrystals

Non-spherical CdSe quantum dots were synthesized through high temperature reduction of cadmium and selenium in the presence of TOP (tri-n-octylphosphine) and TOPO (tri-n-octylphosphine oxide). The high affinity of phosphine oxide to the surface of CdSe nanocrystals typically leads to the formation of spherical particles with diameters between 1.5 and 10 nm. However, with lower temperatures and longer reaction times relative to conventional synthesis techniques, the formation of non-spherical nanocrystals dominated. The three reaction temperatures that were studied were 230, 250, and 270 °C. Results verify the need to quench CdSe nanocrystals immediately following the injection of selenium dissolved in TOP (TOPSe) if spherical particles are the desired shape. Nanocrystal shape evolves from sphere to rectangle to hexagon or triangle as the reaction time is extended regardless of temperature. The highest yield of rectangular particles (~89 %) was achieved while maintaining a temperature of 250 °C for 20 min.