Gold nanoclusters reductively deposited on porous silicon: morphology and electronic structures

Abstract

Utilizing porous silicon as a reducing agent and a substrate, gold complex ions [AuCl4]- were reduced from aqueous solution to produce nanoparticles of gold upon the surface of porous silicon. Scanning electron microscopy (SEM) was utilized to study the morphology of the porous silicon layers and the deposits of gold nanoparticles. It is found that preparation conditions have a profound effect on the morphology of the deposits, especially on porous silicon prepared from a p-type wafer. The gold nanoparticles, varying from micrometric aggregates of clusters of the order of 10 nm, to a distribution of nearly spherical clusters of the order of 10 nm, to strings of ~10 nm were observed and compared to bulk gold metal using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). These techniques confirm and complement the SEM findings. The potential for this reductive deposition technique is noted.Key words: gold nanostructures, reductive deposition, porous silicon, morphology, X-ray spectroscopy.

Permanent Magnetism, Magnetic Anisotropy, and Hysteresis of Thiol-Capped Gold Nanoparticles

“…In Au NPs, a noticeable lattice contraction due to size effect has been observed and reported [6]. The decrease of Au interatomic distances yields enhancement of d-d electron interactions in such a way that the number of d holes decreases respect to that of bulk Au [2]. It has been also shown that in Au NPs capped with strong interacting thiols, the number of holes in the 5d band increases as indicated by the enhanced intensity of the white line feature, arising from 2p 3=2;1=2 !…”

“…Most of these new properties arise from the so-called ''size effect'' which affects the electronic structure, as well as from the increase of the ratio of atoms located at the surface with respect to the total number of atoms of the NP [1,2]. Monodispersed gold particles with an average size below 2 nm have been synthesized by different routes using ligands and surfactants as protective agents [3][4][5].…”

Reductive deposition of Au3+(aq) on oxidized silicon surfaces

“…As a result the claim of Coulthard et.al. (8) that porous silicon is utilized as a reducing agent for reductive deposition of gold must be interpreted as the porous silicon providing ample active sites. This point is further supported by our observation that this deposition even takes place on relatively inert and hydrophobic substrates like polyethylene and (or) polypropylene as shown in Fig.…”

“…The same group later reported on the uptake of gold and palladium from acidic solution of AuCl 3 and PdCl 2 using electroactive polymer-SiO 2 nano-composites (7). In a recent study it was claimed that porous silicon could be utilized for reductive deposition of gold nano-clusters again from an aqueous solution AuCl 4 - (8). In our XPS investigation of metal ions deposited on the surface of silica tubes for atom-trapping atomic absorption spectrometric determinations, we had also reported that Au was deposited in its zerovalent state both from the vapour phase of the flame and also from the aqueous solution of AuCl 4 - (9).…”

Deposition and stability of metal ions on oxidised silicon surfaces: electrochemical correlation

“…Electroical (vapour) deposition of metals and / or their salts less and reductive deposition of Pd, Ag, Pt, Au and onto various surfaces have always been important in Cu from aqueous solutions of their corresponding fields involving semiconductors, coatings, catalysis, ions on porous silicon have been reported [5][6][7][8]. In solar energy applications, etc.…”