High-Temperature Synthesis of CdSe Nanocrystals in a Serpentine Microchannel: Wide Size Tunability Achieved under a Short Residence Time

Abstract

A three-dimensional serpentine microchannel was applied in the reaction part of a microreactor for the synthesis of CdSe nanocrystals (NCs). The local fluctuation of velocity in the turns created by the continuous variation of channel geometry was demonstrated to be effective to maintain a uniform residence time and monomer concentration for the constrained fluid under fast flow rates. Therefore, an enhanced growth rate for NCs within a narrow size distribution was accomplished with a short residence time. The triple-ligand system (trioctylphosphine oxide−oleic acid−oleylamine) was demonstrated to be powerful to achieve high-quality CdSe NCs with a short reaction time. The superior kinetic control achieved via the variation of precursor concentration and Se/Cd ratio provided effective control of the size of CdSe NCs, which allowed the rapid synthesis (8−10 s) of CdSe NCs in a wide size range with diameters ranging from 2.1 to 4.0 nm, while maintaining excellent color purity and a high photoluminescence (P...