Change in Rate of Catalytic Growths of Nanocrystals Catalyst for Formation of Asymmetric Multicomponent Heterostructures and Their Self-Assembly

Abstract

Superionic conductor type catalytic growths leading to dual semiconductor heterostructures are typically carried out above the phase transition temperature of the catalyst. For the case of Ag2S, the room temperature α or monoclinic phase is transformed to β or cubic phase at above 170 °C, and this behaves like a superionic conductor and catalyzes the growth of groups II–VI semiconductors. However, instead of pure Ag2S, while Ag(0)–Ag2S coupled structures are used as catalysts, the triple material heterostructure is formed with ZnS incorporation (Ag–Ag2S–ZnS) which showed a controlled and regulated catalytic growth. The rate was initially observed to be slower, and with the progress of reaction it turned faster, leading to tapered type heterostructures. These nanostructures having the catalyst heads and sharp ZnS tails also showed very unique pattern head-to-head and tail-to-tail self-assembly. Details of the changes in rate of the catalytic growth with the dual structure catalyst and the impact of Ag(0) for obtaining the asymmetric structures are studied and reported. The insight mechanism proposed here for such superionic conductor catalytic growth leading to tapered nanostructures remains a new fundamental for understanding the solid–solution–solid type catalytic growth of nanostructures in solution.