Spatially resolved monitoring of aqueous CdS nanoparticle synthesis in a microreactor

The synthesis of cysteine-capped CdS quantum dot nanocrystals (CdS-cys) between two interdiffusing reagent streams in a continuous flow microfluidic reactor was investigated. Spatially resolved fluorescence imaging and spectroscopy of the microreactor at various reactant concentrations and flow rates was used to study nucleation and growth of these particles. The laminar flow of the impinging streams allowed for controlled diffusional mixing of the reacting cadmium and sulfide ions at the boundary between the two solutions, while the capping agent was present in one or both of the solutions in excess. The results show that the photoluminescence of these particles grown under these microfluidic conditions differs from those grown in batch reactors.