Continuous Synthesis of Full-Color Emitting Core/Shell Quantum Dots via Microreaction

Abstract

A two-step, microreaction system, operating at two different temperatures and incorporating three-dimensional, serpentine microchannels, was used for the continuous synthesis of CdSe/ZnS and CdS/ZnS nanocrystals. By varying the feed ratios of the precursors, we were able to control the size of both CdSe and CdS nanocrystals (NCs) at a constant temperature and residence time. The application of zinc diethyl dithiocarbamate as a single molecular source allowed the preparation of high-quality, ZnS-capped NCs at 140 °C, which is much lower than the temperatures required for the growth of CdS and CdSe NCs. Furthermore, the size-dependent, optimal reaction time for ZnS capping was obtained. The above results facilitated the continuous synthesis of core/shell NCs with photoluminescence wavelength in a wide range. On the basis of the continuous adjustment of the feed ratios of the precursors and the online switching of precursors and serpentine channels for ZnS capping, we obtained the continuous synthesis of full-color-emitting CdS/ZnS and CdSe/ZnS NCs (full-width-at-half-maximum: 25−33 nm; quantum yield: blue - 41%, cyan - 58%, green - 70%, yellow - 78%, orange - 76%, red - 61%).