Synthesis of small silver nanocubes in a hydrophobic solvent by introducing oxidative etching with Fe(III) species

The role of oxidative etching in the synthesis of noble-metal nanocrystals with a hydrophilic solvent (in particular, ethylene glycol) has been explored in our previous work. In this paper, we demonstrate that the mechanism of oxidative etching could be extended to the synthesis of single-crystal Ag nanocrystals in a hydrophobic solvent such as isoamyl ether. In this case, Fe(III) species in the form of FeCl3 or Fe(acac)(3) had to be introduced into the hydrophobic system as an effective etching agent. The final product contained single-crystal Ag nanocubes (slightly truncated) with an edge length as small as similar to 13.5 nm, a size that has been difficult to achieve using a hydrophilic system. The role of oxidative etching in the synthesis of noble-metal nanocrystals with a hydrophilic solvent (in particular, ethylene glycol) has been explored in our previous work. In this paper, we demonstrate that the mechanism of oxidative etching could be extended to the synthesis of single-crystal Ag nanocrystals in a hydrophobic solvent such as isoamyl ether. In this case, Fe(III) species in the form of FeCl3 or Fe(acac)(3) had to be introduced into the hydrophobic system as an effective etching agent. The final product contained single-crystal Ag nanocubes (slightly truncated) with an edge length as small as similar to 13.5 nm, a size that has been difficult to achieve using a hydrophilic system.NSF [DMR-0804088, ECS-0335765]; NIH [DP1 OD000798]; China Scholarship Counci

Seed-Mediated Synthesis of Truncated Gold Decahedrons with a AuCl/Oleylamine Complex as Precursor

A seed-mediated growth method is described for the synthesis of a novel type of Au nanoparticles-truncated decahedrons with a pentagonal, platelike structure (see figure). The precursor is based on the AuCl/oleylamine complex. TEM analyses reveal that the truncated Au nanoparticle has two types of truncation: one is parallel to the five-fold axis and the other is perpendicular to the five-fold axis.NSF [DMR-0804088, ECS-0335765]; NIH [DP1 OD000798]; China Scholarship Counci

Au@Ag Core-Shell Nanocubes with Finely Tuned and Well-Controlled Sizes, Shell Thicknesses, and Optical Properties

This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13 4-50nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride(CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1 2 to 20 nm by varying the ratio of AgNO3 precursor to Au seeds We also investigated growth mechanism by examining the effects of seeds (capped by CTAC or cetyltrimethylammonium bromide (CTAB)) and capping agent (CTAC vs CTAB) on both size and shape of the resultant core-shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au Seeds and Au@Ag core-shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value of ca 3 nm for the shell thickness at which the plasmon excitation of the Au cores would completely screened by the Ag shells. Moreover these Au@Ag core-shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.NSF [DMR 0804088, ECS 0335765]; NIH [1R01 CA138527]; Ministry of Education Science and Technology [R32 20031]; China Scholarship Counci