Size and Morphology Adjustment of PVP-Stabilized Silver and Gold Nanocrystals Synthesized by Hydrodynamic Assisted Self-Assembly

Abstract

A novel process, i.e., ultrasound-assisted membrane reduction, was introduced and applied to synthesize Ag and Au nanocrystals. High-resolution transmission electronic microscopy and UV-vis spectra were adopted to observe and study the resulting colloids. The nearly spherical Ag and Au nanoparticles with mean diameters of 5.8 and 6.8 nm, respectively, were synthesized with the novel method. The silver nitrates/hydrogen tetrachloroaurate hydrate, sodium borohydride, and poly(N-vinyl-2-pyrrolidone) (PVP) were used as metal precursor, reductant, and stabilizer, respectively. The reverse mixing of silver nitrate and reductant resulted in larger Ag nanoparticles in the range of 5-24 nm. The addition of ethylenediaminetetraacetic acid (EDTA), which may serve as the second protecting agent together with PVP, could reduce the Au particle size to a mean value of 2.6 nm. By varying the NaBH 4 injection rate in the process, a portion of the primary Au crystallites could be self-assembled to form decahedral Au nanocrystals with a diameter of ca. 24 nm. The two-dimensional networked gold nanowires with mean diameters of 5-10 nm could be fabricated by regulating the acidity of the reaction system to pH 10 with aqueous ammonia.

A one-pot synthesis of colloidal Ag–Au nanoparticles with controlled composition

“…In this paper we report a simple and single-step approach to the preparation of bimetallic Ag-Au colloids that employs Na 2 EDTA, which simultaneously acts as a reductant and an effective agent for regulating the composition of obtained nanoparticles. While synthetic protocols for the preparation of nanoparticles consisting of individual gold or silver using Na 2 EDTA (or EDTA) are relatively well-known [20][21][22][23][24][25], Na 2 EDTA-based syntheses of bimetallic Ag-Au nanoparticles have not yet been reported in the literature.…”

Shape-controlled synthesis of silver particles by surfactant self-assembly under ultrasound radiation

“…Static, hard and soft templates have been, respectively, used to enhance the growth rate of one crystallographic face over another (Cho 1999;Zhao et al 2004;Hu et al 1999), anisotropic growth (Huang et al 2000) and synthesis of different shape of particles (Pileni 2003;Suber et al 2005;Ding et al 2008;Wei 2006;Eastoe et al 2006). Within all these methods, surfactant selfassembly has been widely reported because of its superior ability in controlling the size (Jana et al 2001;Kovalenco et al 2007) and morphology (Jana et al 2001;Kovalenco et al 2007;Wang et al 2002;Johnson et al 2002;Liu et al 2009;Nishino and Kanno 2008) of nanoparticles. In the present work, self-arrangement property of the surfactant as a template has been investigated to produce different shapes of particles such as cubic, porous micro-rod, sphere and dendrite forms under ultrasound radiation.…”

Gold nanoparticle/polymer nanofibrous composites by laser ablation and electrospinning

“…In this study, the gold nanoparticles (Au-NPs) were formed directly in the 15% (w/v) PVP solution by laser ablation of a solid gold block. PVP was chosen for a couple of reasons; (i) the electrospinning of the PVP nanofibers is very easy, and PVP has been shown to be a good fibrous matrix for incorporation of metal NPs [13,14], (ii) PVP is a water soluble polymer having a hydrophilic nature and it is widely used as a stabilizer and capping agent for Au-NPs and therefore protect the NPs from agglomeration in the medium [15,16].…”