Synthesis of Pt Double-Walled Nanoframes with Well-Defined and Controllable Facets

Abstract

In this paper, we demonstrate the synthesis of morphologically complex nanoframes wherein a mixture of frames and thin solid planes, which we refer to as walled-nanoframes, are present in a single particle. By applying multiple chemical steps including shape evolution of Au nanocrystals and controlling chemical potential of solution for selective deposition, we successfully designed a variety of Pt nanoframes including Pt cuboctahedral nanoframes and Pt single-walled nanoframes. The rationale for on-demand chemical steps with well-faceted Au overgrowth allowed for the synthesis of double-walled nanoframes where two Pt single-walled nanoframes are concentrically overlapped in a single entity with a clearly discernible gap between the two nanoframes. Given the coexistence of an open structure of nanoframe and thin plates within one entity, the double-walled nanoframes showed a dramatic increase in catalytic activity toward the methanol oxidation reaction, acting as high-surface area, carbon-free, and volume-compact nanocatalysts.

Plasmonic Double-Walled Nanoframes with Face-to-Face Nanogaps for Strong SERS Activity

“…Mainly, shape evolution of Au nanocubes to Au cuboctahedrons (step 1), facet-selective Pt deposition via controlling the chemical reduction potential of Pt (step 2), well-faceted Au growth (step 3), selective Pt deposition again (step 4), etching of inner Au (step 5), and regrowth of Au (step 6) are applied on demand following our previous protocol. 21 To briefly explain, first, in the shape transformation process, Au nanocube seeds with six (100) facets undergo a layer-by-layer growth by codeposition of Au 3+ and Ag + and are transformed into the Au cuboctahedrons composed of a mixture of six (100) and eight (111) facets with an increase of particle size (Supporting Information (SI), Figure S1). If the growth further proceeds, Au octahedrons with eight (111) facets are formed.…”

Three-Dimensional Au Octahedral Nanoheptamers: Single-Particle and Bulk Near-Field Focusing for Surface-Enhanced Raman Scattering

“…The Pt shell serves as a protective layer, preventing the etching of the inner Au. Then, well-faceted overgrowth of Au is achieved through epitaxial deposition (step 2), resulting in the formation of octahedral shapes with well-defined crystallographic facets under codeposition of Au and Ag ions. , This step is based on the difference in surface energy among the edges, vertices, and terraces of the Au octahedron. In step 3, with the assistance of Ag, Pt 4+ ions are selectively reduced on the sharp edges of an Au octahedron due to the difference in surface energy between the terraces and edges of the Au, leading to the formation of an Au@Pt edge octahedron. , In step 4, the inner Au octahedron is etched by Au 3+ through comproportionation of Au + , leaving the Au nanosphere-core Pt-octahedral-frame-shell that resembles a cage-bell nanostructure.…”

Step-by-Step Nanoscale Top-Down Blocking and Etching Lead to Nanohexapods with Cartesian Geometry

“…When the Au@Pt TOHs with Pt masking both {100} facets and the edges were used (Figure S8A), walled Pt nanoframes were produced, as we recently reported. 40 When the Au@Pt edge TOHs where the Pt atoms were selectively deposited along the edge of TOHs were adopted for the inner Au etching process, etching occurred through all the faces of Au@Pt edge TOHs because no Pt masks fully covered the facet, hindering the generation of the hexapod-like morphology (Figure S8B). In the case of bare Au TOh, because there were no blocking masks on the surface, etching proceeded throughout the whole surface without any preference, resulting in the Au nanospheres with smooth surfaces (Figure S8C).…”