Transforming Noble‐Metal Nanocrystals into Complex Nanostructures through Facet‐Selective Etching and Deposition

Abstract

Facet-selective etching and deposition, as determined by the landscape of surface energy, represent two powerful methods for the transformation of noble-metal nanocrystals into nanostructures with complex shapes or morphologies. This review highlights the use of these two methods, including integration of them, for the fabrication of novel monometallic and bimetallic nanostructures with enhanced properties. We start with an introduction to the role of surface capping in controlling the facet-selective etching or deposition on the surface of Ag nanocrystals, followed by a case study of how to maneuver etching and deposition at different facets of Pd nanocrystals for the fabrication of nanoframes. We then introduce the use of galvanic replacement to accomplish selective etching and deposition on two different facets in an orthogonal manner, transforming Pd nanocubes into PdÀ Pt octapods. By complementing galvanic replacement with a chemical reduction reaction, it is also feasible to control the rates of these two reactions for the conversion of Ag nanocubes into Ag@AgÀ Au concave nanocubes and Ag@Au core-shell nanocubes. These transformation methods not only greatly increase the shape diversity of metal nanocrystals but also offer nanocrystals with enhanced plasmonic and/or catalytic properties.[a] J.

Understanding the Impact of Sulfur Poisoning on the Methane-Reforming Activity of a Solid Oxide Fuel Cell Anode

“…This can be achieved on nanostructured noble-metal surfaces, − where the localized surface plasmon resonance (LSPR) causes molecules in the vicinity to polarize to a greater magnitude. Such a phenomenon is referred to as surface-enhanced Raman scattering, and for decades it has served as a beneficial strategy to enhance Raman intensities. ,, Accordingly, in this study, we employed Ag@SiO 2 SERS nanoprobes to tackle the challenges commonly encountered with normal Raman spectroscopy (Figure e). By isolating the Ag plasmonic core with a thin SiO 2 shell, we created shell-isolated nanoprobes that are not only highly efficient when used to amplify the analyte detection sensitivity but also electrocatalytically inert and thermally stable up to 500 °C. ,, The enhancement factor (EF) of the Ag@SiO 2 nanoparticles was estimated using Rhodamine 6G (R6G) dye as a probe molecule (Figure S8) as follows , where I SERS is the Raman peak intensity of the R6G (1646 cm –1 ) measured with Ag@SiO 2 and I blank is the Raman peak intensity of R6G without SERS nanoprobes.…”

“…Such a phenomenon is referred to as surfaceenhanced Raman scattering, and for decades it has served as a beneficial strategy to enhance Raman intensities. 35,66,67 Accordingly, in this study, we employed Ag@SiO 2 SERS nanoprobes to tackle the challenges commonly encountered with normal Raman spectroscopy (Figure 2e). By isolating the Ag plasmonic core with a thin SiO 2 shell, we created shellisolated nanoprobes that are not only highly efficient when used to amplify the analyte detection sensitivity but also electrocatalytically inert and thermally stable up to 500 °C.…”

Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors

“…Nanoscale galvanic replacement is an electrochemical process that occurs when a metal ion encounters a nanoparticle made of a zero‐valent metal with a lower redox potential (often referred to as the sacrificial template), leading to an exchange of electrons by which the template metal will be oxidized and dissolved while the oxidant metal ion is reduced onto the surface of the template metal, leaving behind a shell mirroring the selected template's original size and shape . The extent of alloying to dealloying dictates the composition, thickness, porosity and structural integrity of the walls, and as the galvanic exchange proceeds, dealloying may occur and lead to a cage‐like structure followed by the collapse of the nanoparticle into fragments .…”

Noble-Metal Nanoframes and Their Catalytic Applications

“…Heterogeneous catalysis built around noble-metal nanocrystals is central to the chemical, energy, and automobile industries. − Over the past several decades, nanocrystals made of Pd, Pt, Rh, Ru, Ir, Ag, and Au and combinations of those have received great interest owing to their favorable electronic structures for achieving high catalytic activity and/or selectivity toward a broad spectrum of reactions. These materials often exhibit their resistance to corrosion for sustaining long-term durability in a wide variety of catalytic processes. − However, because of their extraordinary low abundances in the Earth’s crust and the ever-increasing demands from various industries, there is an urgent need to utilize this extremely rare resource in a cost-effective and sustainable manner without compromising the catalytic performance. To this end, it is pivotal to maximize the mass-based catalytic activity of the noble-metal nanocrystals.…”