A Wulff in a Cage: The Confinement of Substrate-Based Structures in Plasmonic Nanoshells, Nanocages, and Nanoframes Using Galvanic Replacement

Abstract

Galvanic replacement reactions carried out on solid core-shell structures typically yield a noble metal nanorattle geometry in which a mobile core is contained within a hollowed shell. Here, we adapt this colloidal synthesis to substrate-based structures to obtain a fundamentally altered product in which an immobilized core is separated from the shell by a well-defined gap, an architecture unobtainable using colloidal techniques and that offers unique advantages in terms of generating plasmonic near-field effects within the confines of a single structure. In the devised route, Wulff-shaped templates of Au, Pt, or Pd, formed through the dewetting of ultrathin films, are first transformed into core-shell structures through the reduction of Ag(+) ions onto their surface and then further transformed through the galvanic replacement of Ag with Au. Through suitable adjustments to the shell geometry, the epitaxial relationship with the substrate, and the extent to which the shell is replaced, it is possible to generate an entire family of nanostructures in which a Wulff-shaped core is confined within a nanoshell, nanocage, or nanoframe, where, in all cases, bonds formed between the structure and the substrate preclude motion. With the potential to tune the gap width, the geometry of the confining structure, and the composition of the core, shell, and substrate, these structures could find application as catalytic nanoreactors able to drive both single-step and cascade reactions or as plasmon-based sensing elements for biological and chemical detection.

Copper Template Design for the Synthesis of Bimetallic Copper–Rhodium Nanoshells through Galvanic Replacement

“…The XRD data, when correlated with the observed faceting relative to the substrate alignment flat, indicates that the cuboctahedrons have two orientational relationships with the substrate that are given by (111)[–211] Cu ∥(0001)[11–20] sapphire and (111)[21–1–] Cu ∥(0001)[11–20] sapphire . These relationships are in agreement with those observed for Au[23a] and Pd nanostructures on sapphire. Neither the spherical seeds nor the cuboctahedron templates show any peaks corresponding to Cu 2 O or CuO.…”

“…The oxidation of Cu nanostructures has been well‐documented by monitoring its deleterious influence upon the plasmon resonance,[19f,20a,22] which over an extended period of time sees the plasmon peak extinguished. In previous studies, we have demonstrated the galvanic replacement of substrate‐supported templates formed in the vapor phase . Here, we demonstrate a related synthetic scheme for the formation of highly faceted substrate‐supported Cu templates and their subsequent transformation into the CuRh shells using aqueous galvanic replacement reactions.…”

The Design and Synthesis of Hollow Micro‐/Nanostructures: Present and Future Trends

“…The length of nanothorns can be easily tailored by controlling the amount of ethanolamine in the reaction system. Similar to hollow structures with intact surface, these open structures could also be utilized as containers to incorporate core materials . For example, Neretina and co‐workers reported the synthesis of Wulff‐shaped nanostructures confined within nanoframes through solution‐based growth modes on substrate‐based templates .…”

“…Similar to hollow structures with intact surface, these open structures could also be utilized as containers to incorporate core materials . For example, Neretina and co‐workers reported the synthesis of Wulff‐shaped nanostructures confined within nanoframes through solution‐based growth modes on substrate‐based templates . As presented in SEM images, Wulff‐shaped Pt nanoparticle can be incorporated into a Wulff‐shaped or cube‐shaped Ag nanoframe after a sequential coating and selective etching process (Figure k,l).…”

“…Copyright 2016, Wiley‐VCH. k,l) Reproduced with permission . Copyright 2016, American Chemical Society.…”