Gold Nanowire Networks: Synthesis, Characterization, and Catalytic Activity

Abstract

Gold nanowire networks (AuNWNs) with average widths of 17.74 nm (AuNWN(1)) or 23.54 nm (AuNWN(2)) were synthesized by direct reduction of HAuCl(4) with sodium borohydride powder in deep eutectic solvents, such as ethaline or reline, at 40 °C. Their width and length were dependent on the type of solvent and the NaBH(4)/HAuCl(4) molar ratio (32 in ethaline and 5.2 in reline). High resolution transmission electron microscopy (HR-TEM) analysis of the gold nanowire networks showed clear lattice fringes of polycrystalline nanopowder of d = 2.36, 2.04, 1.44, and 1.23 Å corresponding to the (111), (200), (220), or (311) crystallographic planes of face centered cubic gold. The purified AuNWNs were used as catalysts for the chemical reduction of p-nitroaniline to diaminophenylene with sodium borohydride in aqueous solution. The reaction was monitored in real time by UV-vis spectroscopy. The results show that the reduction process is six times faster in the presence of gold nanowire networks stabilized by urea from the reline (AuNWN(2)) than in the presence of gold nanowire networks stabilized by ethylene glycol from ethaline (AuNWN(1)). This is due to a higher number of corners and edges on the gold nanowires synthesized in reline than on those synthesized in ethaline as proven by X-ray diffraction (XRD) patterns recorded for both types of gold nanowire networks. Nevertheless, both types of nanomaterials determined short times of reaction and high conversion of p-nitroaniline to diaminophenylene. These gold nanomaterials represent a new addition to a new generation of catalysts: gold based catalysts.

Gold Nanoparticles in Novel Green Deep Eutectic Solvents: Self-Limited Growth, Self-Assembly & Catalytic Implications

“…The apparent rate constant is proportional to the surface area available for the reaction. These results help to determine the kinetics of the catalysis reaction in relation with the theoretical kinetic modeling [2,24].…”

Enhanced catalytic and SERS activities of CTAB stabilized interconnected osmium nanoclusters

“…The reduction of aromatic nitro groups using excess NaBH 4 in the presence of metal NPs as catalyst has been investigated. 2,[23][24][25] Very recently, shapeselective Au-Ag core-shell nanocrystals have been utilized for catalytic reduction of nitro compounds. 26 Apart from the catalysis reaction, metal NPs were also tested for surface enhanced Raman scattering (SERS) studies.…”

Porosity-moderated ultrafast electron transport in Au nanowire networks

“…In the NWN, the special network structure imposes restrictions to the electron transport, and consequently the energy dissipation away from the excited region. In addition, Chirea et al [21] have observed an increased catalytic activity in similar Au NWN structures. They attributed this behavior on the increased number of "corners and edges".…”

“…Therefore, research regarding electron confinement in anisotropic nanostructures is increasingly pursued [1,14,15]. Recent developments in the growth of more complex, three-dimensional nanostructures [16][17][18] have shown the way for potential applications in nanodevices, nanocatalysis, nanofoams in composite materials [16,[19][20][21], and drug delivery [22]. In such nanomaterials, several open questions emerge pertinent to whether and how the ultrafast dynamical properties will depend on the peculiar shape and structure that in turn may lead to nonisotropic boundary conditions and electron confinement [1].…”