Facet selective etching of Au microcrystallites

Abstract

Selectively, the {100} and {111} facets of Au microcrystallites are etched using a capping method. The specific etchants etch the facets that are free of capping agents and produce crystallites with well-defined corrugation involving high-index microfacets. Such facets exhibit enhanced Raman activity compared to smooth facets. Provide the authors' website if possible. ABSTRACTHigh symmetry crystals, by nature, exhibit isotropic properties. Inducing anisotropy for example by facet selective etching, is considered implausible in face centered cubic (FCC) metals, particularly in gold, which besides being FCC, is also noble. Here, for the first time, facet selective etching of Au microcrystals obtained in the form of cuboctahedrons and pentagonal rods from thermolysis of a gold-organic precursor is reported. The selective etching of {111} and {100} facets has been achieved via a capping method. In this method, tetraoctylammonium cations selectively cap the {111} facets, while Br -ions protect the {100} facets. The exposed facets are oxidized by O2/Cl -, producing a variety of interesting geometries. Facet selective etching of Au microcrystallites is governed only by the nature of the facets as geometry does not seem to play any significant role. Etched surfaces appear rough but a closer examination reveals well-defined corrugations indexable to high hkl values. Such surfaces exhibit enhanced Raman activity.

Scanning Electrochemical Microscopy for the Electroless Deposition of Gold on Natural Pyrite: Effect of Ferric Ions

“…Indeed, after 300 s (Figures F and H), pseudo spherical particles of about 200 nm diameter are observed and progressively grow and coalesce. These observations demonstrate that Fe 3+ significantly affects the structure of gold deposits, probably because of the selective etching of gold by Fe 3+ during the growth process, as already evidenced at the nanoscale ,. This should be further explored with other metals deposition as it is of major importance for all applications in which dendritic growth has to be avoided, as for lithography or battery applications.…”

“…As discussed in the introduction, Fe 3+ could be involved in the process of gold deposition on pyrite. Moreover, if Fe 3+ ions have been shown to selectively etch gold facets in the bulk,, to the best of our knowledge their effect on the gold electrodeposition has never been explored. However since Fe 3+ is also known to accelerate the corrosion of pyrite,, it is proposed here to use the SECM tip to generate locally and simultaneously Fe 3+ from the oxidation of Fe 2+ , and .…”

Large Scale Solid-state Synthesis of Catalytically Active Fe3O4@M (M = Au, Ag and Au-Ag alloy) Core-shell Nanostructures

“…In the case of Fe 3 O 4 @Au-10 (Fig. 5(e)), several hump type structures in the shell layer of gold was visible over the shell, indicating that the gold precursor initially formed nanoparticles during the decomposition step, which further melted or diffused to form a continuous thin film 41 . With the increment of gold precursor as in Fe 3 O 4 @Au-20 (Fig.…”

Understanding of the major reactions in solution synthesis of functional nanomaterials

“…Owing to the term of the different surface energy, oxidative etching is a useful method to show specific selectivity toward different facets. Based on thermodynamics, atoms are expected to nucleate and grow into cuboctahedra (with a nearly spherical shape) composed by (111) and (100) facets to minimize the total surface energy [380][381][382]. In a solution-phase process, the surface free energies can be altered by adsorption of impurities or capping agents, and thus new shapes will be induced.…”