Multicomponent nanostructures based on noble metal nanostructures: Synthesis and formation mechanism of intermetallic compound and core-shell structures

Abstract

In this study, we have synthesized multicomponent nanostructures including intermetallic compounds and core-shell structures based on single-crystalline noble metal nanowires (NWs) and nanoplates via a chemical vapor transport (CVT) method. We found that ordered intermetallic NWs, which consist of Au and Cu elements, can be simply fabricated by topotaxial transformation. These NWs which have single-crystallinity and clean surfaces, are suitable for catalytic applications. Furthermore, we fabricated $Au@Fe_3O_4$ nanoplate structure, composed of metal core and metal oxide shell, and showed that this nanostructure with several μm sized was successfully formed by excellent epitaxial relationship between two materials. Additionally, we reveal that transition metal and transition metal silicide NW can epitaxially grow on various substrates. Horizontal, vertical and freestanding growths in specific orientations were controlled by varying synthetic conditions such as employed substrate type, and their growth mechanisms for compound NWs were demonstrated in detail. In chapter 1, we report the fabrication of ordered intermetallic Au-Cu NWs by a CVT method and their application in interference-free glucose sensing. Ordered intermetallic $Au_3Cu$ and $AuCu_3$ NWs are fabricated simply by supplying the Cu-containing species to pre-synthesized Au NWs. The Au-Cu NWs are single-crystalline, and the composition of NWs can be determined by adjusting the concentration of Cu-containing species. Furthermore, as-synthesized $Au_3Cu$ NW electrodes provide unique electrocatalytic activity for glucose oxidation, allowing us to detect glucose without interference from ascorbic acid. We anticipate that $Au_3Cu$ NWs could be employed as electrochemical glucose sensors, and the present synthesis method can be used to fabricate various ordered intermetallic nanostructures. In chapter 2, we synthesized two-dimensional plasmonic core (Au)/ magnetic shell ($Fe_3O_4$) heterostructures by CVT ...