Semiconductor nanocrystals exhibit quantum confinement effects below a certain size and their optical and electronic properties become size-dependent. Applications of these materials include biosensors, solar cells, and nanoelectronics. The use of templates in the synthesis of semiconductor nanocrystals allows precise control of their shape and size. It also enables easy scale-up for commercial production.

We have developed mesoscopic models that describe the synthesis of zinc selenide nanocrystals in microemulsions and liquid crystals [1-3]. The templates are formed by self assembly of a ternary system that includes a polar solvent, a non-polar solvent, and an amphiphilic block copolymer. The nanocrystals are grown inside the dispersed nanodomains of the templates, e.g. inside the nanodroplets of a microemulsion or the cylindical nanodomains of a liquid crystal. The initial nuclei are formed by a spontaneous and irreversible reaction between a zinc precursor that is dissolved in the dispersed nanodomains of the template and a selenium precursors that is dissolved in the continuous phase and diffuses through the block copolymer layer. The mesoscopic models are based on kinetic Monte Carlo simulations that track the diffusion of the zinc precursor molecules inside a dispersed nanodomain, the formation of zinc selenide clusters (nuclei) by reaction at the interface with the selenium precursor, and the formation of a single nanocrystal in each nanodomain by cluster-cluster coalescence. Parametric studies have been performed to elucidate the effects of particle coalescence efficiency and interfacial flux of the selenium precursor on the evolution of nanoparticle populations and the time required for formation of a single nanocrystal in each domain.

The mesoscopic models are coupled through the interfacial flux of the selenium precursor to macroscopic (PDE-based)reactor-level models that treat the two phases of the template as interpenetrating continua. This multi-scale modeling approach enables optimal reactor design by linking reactor-level operating parameters with particle formation processes taking place inside the dispersed nanodomains of each template.

References

1. G. N. Karanikolos, P. Alexandridis, G. Itskos, A. Petrou, and T. J. Mountziaris, Langmuir 20, 550 (2004).

2. G.N. Karanikolos, P. Alexandridis, R. Mallory, A. Petrou, and T. J. Mountziaris, Nanotechnology, 16, 2372-2380 (2005)

3. G.N. Karanikolos, N.-L. Law, R. Mallory, A. Petrou, P. Alexandridis, and T. J. Mountziaris, Nanotechnology, 17, 3121-3128 (2006).