Investigation of the Exchange Kinetics and Surface Recovery of Cd_xHg_1-xTe Quantum Dots during Cation Exchange Using a Microfluidic Flow Reactor

Detailed analyses of coupled photoluminescence, emission lifetime, and absorption measurements have been made on the products of cation exchange reactions between CdTe nanocrystals and Hg²⁺ salt/ligand solutions in a microfluidic flow reactor and capillary measurement cell to probe the reaction kinetics over the seconds to hours time scale and to establish the influence of the reaction conditions on the spatial distribution of the mixed cations within the resulting Cd_xHg_1-xTe colloidal quantum dots. The establishment of the evolution of the radiative and nonradiative rates allowed the recovery of the emission quantum yield in Cd_xHg_1-xTe quantum dots to be quantified to almost 50% and the necessary time scales to be determined for each set of reaction conditions. The reaction kinetics showed clear indication of a fast surface exchange process followed by a slower internal rearrangement of the cation distribution.