Elsevier

Materials Letters

Volume 61, Issue 1, January 2007, Pages 130-133
Materials Letters

A facile aqueous-phase route for the synthesis of silver nanoplates

https://doi.org/10.1016/j.matlet.2006.04.021Get rights and content

Abstract

A new seed-mediated method for the synthesis of silver nanoplates is reported, in which tannin (C76H52O46) is used to reduce silver salt in aqueous solution. This synthesis is performed at room temperature, and doesn't need any surfactant or polymer to direct the anisotropic growth. The obtained nanoplates exhibit polygonal morphologies and their size can be tuned through adjusting the amounts of seeds. Due to the anisotropic shape feature, the absorption spectra of the nanoplates prove to be quite different from that of spherical nanoparticles.

Introduction

In recent years, controlling the shape as well as size of metallic nanoparticles has been the focus of chemical and material research fields because it provides an effective strategy for tuning the physical and chemical properties of a metal [1]. Thereinto, planar nanostructures of silver have attracted intensive attention due to their unique optical properties [2], [3], [4], [5], and potential applications in various domains such as optical biosensor [6] and metal-enhanced fluorescence [7]. A number of solution-phase approaches have been developed for the preparation of silver nanoplates or nanoprisms, such as photochemical methods [3], [8], [9], [10], [11], templates (octylamine–water bilayer [12] or polystyrene mesospheres [13]) induced synthesis, surfactant [14], [15] or polymer [16], [17], [18], [19] directed synthesis.

Herein, we present a simple aqueous-phase route for the synthesis of silver nanoplates using tannin as a mild reducer for silver salt. This synthesis is a room-temperature, template-free process, and doesn't need any surfactant or polymer to direct the anisotropic growth of the planar nanostructures. Based on these features of the synthetic procedure, “clean” products might be obtained without residual directing agent on their surfaces, which means less interference to their optical properties [20] and is meaningful for sensing applications such as surface-enhanced Raman scattering [21].

Section snippets

Experimental section

First, silver seed was prepared using a similar procedure to that reported in literature [22]: 0.9 ml 10 mM NaBH4 aqueous solution was rapidly injected into 30 ml aqueous solution containing 0.25 mM AgNO3 and 0.25 mM trisodium citrate while vigorous stirring. After 30 s, stirring was stopped, and the seed solution was aged for 2∼3 h before use. Seed diameters should be 3∼5 nm.

Secondly, a set of growth solution was prepared by mixing of 10 ml aqueous solution of AgNO3 (5 mM) and 10 ml aqueous

Results and discussion

Seed-mediated approach has been used to prepare one-dimensional metallic nanostructures [1], [22] and lately developed by Chen et al. to prepare silver nanoplates with ascorbic acid as a reducer [14]. In Chen's synthesis, cetyltrimethylammonium bromide (CTAB) was found to be the key factor for the anisotropic growth since it exerted stronger adsorption on the basal plane than that of the side plane of the nanoplates. In addition, NaOH at proper concentration was necessary for plate formation

Conclusions

Silver nanoplates are prepared through a tannin-reduction process without introducing any surfactant or polymer to direct the two-dimensional growth. The amounts of seed show important influence to the size as well as morphology of the products, and at the fewest amount of seed, silver nanowires could even form in addition to the nanoplates. The synthetic strategy presented here is simple and environmentally friendly, and may provide a promising way for the synthesis of other noble metals with

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