Morphological Evolution of Single-Crystal Ag Nanospheres during the Galvanic Replacement Reaction with HAuCl 4 †

Department of Biomedical Engineering, Washington University, Saint Louis, Missouri 63130.
The Journal of Physical Chemistry C (Impact Factor: 4.77). 02/2008; 112(21):7872-7876. DOI: 10.1021/jp711662f
Source: PubMed


This paper presents a systematic study of the galvanic replacement reaction between 23.5 nm single-crystal Ag nanospheres and HAuCl(4) in an aqueous medium. We have monitored both morphological and spectral changes as the molar ratio of HAuCl(4) to Ag is increased. The replacement reaction on single-crystal Ag nanospheres results in the formation of a series of hollow and porous nanostructures composed of Au-Ag alloys. By varying the molar ratio of HAuCl(4) to Ag, we are able to control the size and density of the pores. In addition, the localized surface plasmon resonance peaks of these nanostructures can be readily tuned from 408 to 791 nm as the product becomes increasingly more hollow and porous.

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Available from: Xianmao Lu, Jan 11, 2014
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    • "As a result, the reaction product can achieve a shape which radically differs from that of the original template. Notable examples include templates which are cuboctahedrons [3] [20] [21], polyhedrons [4], multiply twinned particles (MTP) [15], and nanowires [22]. The early stages of the reaction are characterized by the preferential deposition of Au on facets having high surface energy. "
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    ABSTRACT: The sacrificial templates used in galvanic replacement reactions dictate the properties of the hollow metal nanostructures formed. Here, we demonstrate that substrate-based Au-Ag nanoshells with radically altered properties are obtained by merely coating silver templates with an ultrathin layer of gold prior to their insertion into the reaction vessel. The so-formed nanoshells exhibit much smoother surfaces, a higher degree of crystallinity and are far more robust. Dealloying the nanoshells results in the first demonstration of substrate-based nanocages. Such cages exhibit a well-defined pattern of geometric openings in directions corresponding to the {111}-facets of the starting template material. The ability to engineer the cage geometry through adjustments to the orientational relationship between the crystal structure of the starting template and that of underlying substrate is demonstrated. Together these discoveries provide the framework to advance our understanding of the mechanisms governing substratebased galvanic replacement reactions.
    Full-text · Article · Mar 2014 · Nano Research
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    • "Much work has been reported by Xia et al. on shape-or morphologycontrolled nanostructures such as cubes, spheres, and other porous structures [16] [17] [18] [19] [20]. They have studied the mechanism and morphological evolution of the galvanic replacement reaction [21] [22]. Recently, we extended the replacement reaction method traditionally used to produce solid metals so that it can be used to synthesize metal oxides [23]. "
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    ABSTRACT: An investigation was carried out about the gold nanotube synthesis via a galvanic replacement reaction. The progress of the gold nanotube synthesis was investigated using electron microscopy and UV-Vis spectroscopy. In addition, the reaction rates of gold nanotube formation in the early stage of the reaction were studied. The chlorine ion concentration linearly increased with the gold precursor concentration but deviated from the stoichiometric amounts. This deviation was probably due to AgCl precipitates formed by the reaction of chlorine ions with dissolved silver ions. The replacement reaction was promoted with increased temperature and was nonlinearly proportional to the gold ion concentration. The outcomes of this research will enhance the current understanding of the galvanic replacement reaction.
    Full-text · Article · Jun 2010 · Journal of Nanomaterials
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    ABSTRACT: This paper describes a simple and facile method for the synthesis of Ag/Au bimetallic hollow and porous nanoshells (HPNSs) with controllable porosity, using polycrystalline Ag nanoparticles as starting templates. The optical and catalytic properties of the HPNSs can be easily tuned by using hydrogen peroxide as a mild etchant to controllably dissolve Ag atoms from the precursor Ag/Au bimetallic hollow nanoshells (NSs). The surface plasmon bands of the HPNSs can be easily tuned from the visible to the near infrared (NIR) region. As a model reaction to evaluate the catalytic activity of the HPNSs, we chose the reduction of p-nitrophenol by NaBH4 to afford p-aminophenol. The porous NSs exhibit higher catalytic activity than non-porous NSs even though the latter have higher Au/Ag ratios than the former. Although the composition (Au/Ag ratio) may have some effect, the morphology (porosity) of the HPNSs plays the most important role in the catalysis. The as-synthesized plasmonic HPNSs, due to their facile aqueous-phase preparation, tunable optical properties (in the visible and NIR windows), and unique porous hollow structures, have promising potential applications in various fields ranging from biosensing, nanomedicine (drug/gene delivery, cancer theranostics, etc.), to catalysis and solar cells.
    No preview · Article · Feb 2012 · Nano Research
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