Formation mechanisms of ZnO shells on the surface of CdS nanoparticles in CdS/ZnO Core/Shells

Over the past few years, preparation of a passive surface on semiconductor nanoparticles by applying a layer of inorganic, organic, or bioactive materials in the form of Core/Shell nanocomposites has attracted considerable attention [1]. Most of nano semiconductors properties are highly dependent on their band gap size. Recently, many investigations were carried out for changing band gap of semiconductors via synthesizing of different composite materials in heterostructure forms [2]. Therefore, core/shell nanoparticles based on semiconductor particles have been used to improve optical and catalytic properties, chemical stability and so on. For achieving these purposes, most of semiconductors nanocomposites have been synthesized in Core/Shell form with higher band gap semiconductor used as shell component such as ZnO/CdSe [3], Cds/CdSe [4] and CdSe/SiO2 [5]. Cadmium Sulfide is one of the most important II-VI semiconductors with wurtzite structure and 2.42eV band gap (in bulk state at 25°C). ZnO with hexagonal wurtzite structure and 3.37eV band gap (in bulk state at 25°C) and it is also from II-IV semiconductors [6,7]. The difference in their band gap makes them capable to work in more extended light wave length as photocatalysts