We report a novel approach for the on-line characterization of nucleation and growth kinetics of lead sulfide (PbS) quantum dots using droplet-based microfluidics. Monodisperse NIR-emitting PbS with optical bandgap between 680 to 1200 nm can be formed rapidly using two reaction schemes at different operating temperatures between 70 and 130°C and the temporal evolution of the absorption and fluorescence spectra are monitored in real-time using a microfluidic platform with an on-line absorption and fluorescence optical system. Therefore, this microfluidic platform is able to provide quantitative information on a millisecond (ms) time frame regarding the size, size distribution, concentration and emission characteristics of the generated nuclei and particles. To our knowledge, this represents the first microfluidic approach for the study of the nucleation and growth in high-temperature colloidal crystallization using in-situ absorption and photoluminescence spectroscopy.

Alloyed nanorods and hybrid nanostructures composed of CuInS2 and ZnS were synthesized by heating-up and hot-injection procedures. The synthesis starts with the formation of copper sulfide seeds, which are subsequently converted to copper sulfide – copper indium zinc sulfide hybrid nanostructures, by incorporation of indium and zinc ions. The fraction of ZnS within the alloyed material could be controlled by the amount of the Zn precursor in the reaction solution. In reactions with higher zinc precursor concentrations, at longer reaction times L-shaped hybrid nanostructures are formed of CuInS2-ZnS alloy and ZnS. An additional injection of the Zn-precursor into the reaction solution results in the formation of U-shaped hybrid nanostructures.