Abstract
In this study, we fabricated three-dimensional (3D) hierarchical plasmo-photonic nanoarchitectures by epitaxially integrating semiconducting zinc oxide (ZnO) nanowires with vertically oriented plasmonic gold (Au) and silver (Ag) nanoplatforms and investigated their growth mechanisms in detail. We synthesized 3D hierarchical Au–ZnO nanostructures via a vapor–solid mechanism leading to the epitaxial growth of ZnO nanowires on vertically oriented single-crystalline Au nanowires on a strontium titanate (SrTiO3) substrate. The elongated half-octahedral Au nanowires with a rhombus cross-section were transformed into thermodynamically stable elongated cuboctahedral Au nanowires with a hexagonal cross-section during the reaction. After the transformation, ZnO thin films with six twinned domains were formed on the side planes of the elongated cuboctahedral Au nanowire trunks, and six ZnO nanowire branches were grown on the ZnO thin films. Further, 3D hierarchical Ag–ZnO nanostructures were obtained via the same vapor–solid mechanism leading to the epitaxial growth of ZnO nanowires on vertically oriented Ag nanoplates on an aluminum oxide (Al2O3) substrate. Therefore, the growth mechanism developed herein can be generally employed to fabricate 3D hierarchical plasmo-photonic nanoarchitectures.
Highlights
Hierarchical Ag–zinc oxide (ZnO) nanostructures were obtained via the same vapor–solid mechanism leading to the epitaxial growth of ZnO nanowires on vertically oriented Ag nanoplates on an aluminum oxide (Al2 O3 ) substrate
We believe that 3D hierarchical Au–ZnO and Ag–ZnO nanostructures could possess much higher efficiency than ZnO nanostructures in photovoltaic and photocatalytic applications owing to the large roughness factor, fast electron transport, and the improved optical absorption arising from plasmonic effects of Au and Ag
ZnO thin films with six twinned ZnO domains were formed on the side planes of the elongated cuboctahedral Au nanowire trunks, and six ZnO nanowire branches were grown on the ZnO thin films
Summary
Three-dimensional (3D) hierarchical nanoarchitectures have various exceptional physical and chemical properties owing to their unique structures; they are used as advanced materials for various applications, including catalysis [1,2,3,4], optoelectronics [5], spintronics [6], and thermoelectrics [7]. 3D hierarchical nanoarchitectures in which all nanostructures are integrated epitaxially can exhibit innovative functionalities because dissimilar properties of different nanomaterials can be effectively combined due to perfect epitaxial bonding between nanomaterials. Synthesizing epitaxially integrated 3D hierarchical metal–semiconductor hetero-nanostructures is quite challenging due to the lack of appropriate growth mechanisms. To the best of our knowledge, there is no report on the synthesis of epitaxially integrated 3D hierarchical metal–semiconductor hetero-nanostructures
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