Sn-catalyzed ZnO nanodendrite array

1. A systematic study on metal-catalyzed Vapor-liquid-solid (VLS) process of metal-oxide nano-dendrites Pu-Xian Gao, Department of Chemical, Materials and Biomolecular Engineering & Institute of Materials Science, University of Connecticut • The advance of fundamental understanding are necessary on the influence of metal catalyst on the VLS growth process of metal oxide nanodendrites, considering their growing potentials as next generation of nanomaterials candidates for petrochemical, energy, and environmental applications. The combining effect from metal catalyst, intrinsic metal oxide crystallography, and substrate/nanostructure interfaces is far from clear compared to the VLS growth phenomena itself. Growth kinetics control can greatly influence the combining effect, i.e., the eventual growth product in the form of nanodendrite. A significant progress in this regard is that we successfully grow dendritic ZnO nanostructures both with and without using metal catalysts such as Sn. Behind that, the crystal orientation relationship between the core nanowires and dendritic nanobranches can be governed by the growth kinetics. Comparing with the normal dendrite growth process between ~1100 oC -1400 oC, at the low temperature range between ~500 oC -1000 oC, the multi-crystal ZnO dendritic growth becomes more popular in both Sn-catalyzed and self-catalyzed VLS growth processes. As another important growth kinetics parameter, pressure could play a counter-interactive role from temperature, which needs further investigation. The Other notable outcomes from these studies include: • Intermediate (2nd) metal catalyst (Ag) induced chemistry changes (growth of Zn2SnO4 nanowires) • Confirmation of an oxide catalyzed vapor-solid-solid (VSS) growth process in single crystalline Zn2SnO4 nanowires at ~650 oC, instead of a VLS process at high temperature (~1000 oC, literature). • Large scale synthesis of Zn2SnO4 nanowires on Ag coated Si substrates • A new growth model for Zn2SnO4 nanowires: two-dimensional nucleation and periodic ledge growth model • Ethanol/oxygen sensing mechanism using Ag2O/Zn2SnO4 hybrid nanowire film Sn-catalyzed ZnO nanodendrite array ZnO multi-crystal nanodendrite ZnO single-crystal nanodendrite Zn2SnO4 single-crystal nanowires