Cadmium selenide and zinc sulfide nanoparticles - challenges in synthesis revealed through optical properties

Semiconductor nanoparticles, also called quantum dots (QDs), are emerging as the new class of fluorescent labeling materials in biological applications. In comparison with fluorescent dyes, QDs have unique optical and electronic properties: size-tunable light emission, high brightness, broad excitation with possible simultaneous excitation of multiple fluorescent colors. One of the key challenges for synthesis chemistry is to produce small size and monodisperse (single color) QDs with high reproducibility. In this report we describe synthesis and characterization of CdSe and ZnS QDs using two different synthesis approaches. The first is carried out at high temperature in trioctyl-phosphine oxide (TOPO) as a coordinating solvent, while the second synthesis is carried out at lower temperature in ethylene glycol. We present the challenges in nanoparticle synthesis and show ways, in which these could be overcome