Technical Proceedings of the 2014 Clean Technology Conference and Trade Show

Cleantech 2014

Chapter 10: Nanoscale Materials

R. Dvorsky, P. Praus, L. Svoboda, D. Matýsek, T. Dropa, J. Trojková, K. Šollová
VŠB-Technical University of Ostrava, CZ
411 - 413
nanoparticle, silicon, ZnS, core-shell, photocatalytic, vacuum freeze-drying
For easy handling in some practical processes, active nanoparticles are usually deposited on surfaces of larger carrier particles. In our previous work, the particles of montmorillonite MMT with a mean size of 300 nm served as carriers for individual photocatalytic ZnS nanoparticles, prepared by precipitation in the presence of CTAB surfactant, limiting their size to less than 4 nm. In this subsequent work, we present the first results of new method of creating a thin ZnS shell on silicon carrier nanoparticles via the reactive synthesis on the interface of solid Zn(OAc)2 shell and gaseous H2S. The carrier Si nanoparticles in an aqueous dispersion had the maximum size fraction at 56,6 nm checked by the TEM image analysis. Then, the appropriate amount of Zn(OAc)2 reactant was added to dissolve in the dispersion which, for the given total area of Si–H2O interface, produces the desired thickness of the future ZnS shell. After intense sonication and rapid freezing, the dispersion solution was desiccated by controlled vacuum freeze-drying. The surface temperature during the sublimation was adjusted to -23 ˚C to enable self-organization of the sublimate into mostly single-layer lamellar agglomerates of Si nanoparticles with a thin Zn(OAc)2 reactant coating. This intermediate lamellar
Preparation of Photocatalytic Silicon Core-shell Nanoparticles Covered by ZnS Shell in Solid-Gas Reaction