Au@Ag Nanoparticles: Halides Stabilize {100} Facets

Abstract

Seed-mediated growth is the most efficient methodology to control the size and shape of colloidal metal nanoparticles. In this process, the final nanocrystal shape is defined by the crystalline structure of the initial seed as well as by the presence of ligands and other additives that help to stabilize certain crystallographic facets. We analyze here the growth mechanism in aqueous solution of silver shells on presynthesized gold nanoparticles displaying various well-defined crystalline structures and morphologies. A thorough three-dimensional electron microscopy characterization of the morphology and internal structure of the resulting core–shell nanocrystals indicates that {100} facets are preferred for the outer silver shell, regardless of the morphology and crystallinity of the gold cores. These results are in agreement with theoretical analysis based on the relative surface energies of the exposed facets in the presence of halide ions.

Au@Ag core/shell cuboids and dumbbells: Optical properties and SERS response

“…The formation of dumbbellshaped Au@Ag NRs suggests that the {111} facets of the AuNRs are more accessible to silver atoms than the {110} facets, in which densely packed CTAC assemblies were formed. In contrast, during the slow reduction of silver ions at high temperature (60 1C) and without the addition of NaOH, favored growth of a silver layer on the higher index lateral facets has been reported [29,37,38]. Fig.…”

“…Controlling the thickness and preferred facets of the overgrown Ag shell determines the final shape of nanoparticles and their plasmonic properties [37]. The shape transformation can further affect the electromagnetic field distribution around nanoparticles and, consequently, affect their SERS response.…”

Colloidal nanoparticles as advanced biological sensors

“…2C) (34). For example, density functional theory (DFT) has been used in combination with three-dimensional electron microscopy to study the growth of Ag shells on Au nanoparticles, revealing that growth on the (100) facets is preferred regardless of the morphology and crystallinity of the Au core (35). DFT has also been used to study the effect of alkanethiol capping ligands of different lengths on the shape evolution of AuNPs during colloidal growth, showing that ligand concentration on particular faces drives variations in morphology (26).…”

Rational selection of halide ions for synthesizing highly active Au@Pd nanobipyramids

“…35,36,45 Very recently, several groups demonstrated that the optimized synthesis of Au seeds allows for the direct preparation of high-quality Au NBs without the use of shape-selective precipitation. 33,48,49 However, for other metals, the syntheses of NBs have been rarely reported. As described above, Pd-based nanostructures are potential catalysts for many organic reactions and fuel cells, [10][11][12][13][14][15][16][17][18] and therefore, it is worth developing methods that can be used to prepare Pd NBs, and explore their catalytic performance.…”