Electrochemical Deposition Of Gold Research Articles

Facile electrodeposition of flower like gold nanostructures on a conducting polymer support.

Herein, we report an attractive, simple and templateless synthetic method for the formation of anisotropic gold nanostructures. Gold 'mesoflowers' consisting of arrays of nanoplatelets were synthesized by electrochemical gold deposition on/off conditions onto a conducting poly(diphenylamine) (PDPA) support matrix. A possible forming mechanism of anisotropic gold nanostructures is presented. The electronic and electrochemical properties of gold nanoflower decorated PDPA in an assembled diode configuration were evaluated.

Electrochemical Deposition of Gold-Tin Alloy from Propyleneglycol Electrolyte

Stable and simple in composition nonaqueous propyleneglycol (PG) electrolyte containing tetracyanoaurate(III) and tin(IV) chloride pentahydrate in mole ratio 1:14 has been developed for the electrochemical deposition of gold–tin alloy with the elemental, phase composition and microstructure acceptable for soldering in electronics. This electrolyte provides deposition of Au–Sn coatings at a rate of 2.4 mg/cm2·h (1.8 µm/h accounting the alloy composition) and to obtain alloys which consist of Au5Sn and AuSn crystalline intermetallics containing 14–67 at.% of tin (optimal 39 at.%) in total that corresponds to the composition of eutectic applicable as a solder. Coatings have a very uniform tightly packed and fine-grained microstructure and are composed of spherical grains 0.1–1.0 µm in diameter and average size of 0.2 µm. The addition of water or full change of PG on water fastens the rate of coating deposition and stipulates the formation of coatings with mush less tin content, more coarse-grained microstructure and predominance of gold or gold-enriched intermetallics in their phase composition. The effect of the electrolyte composition and the regime of its work on the elemental and phase composition of coatings, their microstructure and the rate of deposition have been determined. The role of PG in the process of mutual gold and tin electro-reduction and intermetallic compounds crystallization has been found out.

Batch fabrication of gold–gold nanogaps by E-beam lithography and electrochemical deposition

We report on the successful development of a well-controlled two-step batch nano-fabrication process to achieve nanometer-size gaps at the wafer scale. The technique is based on an optimized electron-beam lithography process, which enables the fabrication of nanogaps in the range (15 ± 4) nm. Following this first step, the feedback-controlled electrochemical deposition of gold from an aqueous HAuCl4-based electrolyte is applied to further reduce the size of the gap down to about 0.3–1.0 nm. This protocol was successfully demonstrated by fabricating more than 385 nanogaps on a 4 inch wafer. The reproducible fabrication of nanogaps in the range between 0.3 and 1.0 nm opens up new perspectives for addressing the electrical and reactivity properties of single molecules and clusters in confined space under well-controlled conditions.

Electrochemical synthesis of gold nanorods in track-etched polycarbonate membrane using removable mercury cathode

The electrochemical template synthesis of gold nanorods within the cylindrical pores of track- etched polycarbonate (PC) membrane using a remov- able mercury cathode is reported. The novelty of this new approach is that it eliminates the requirement of coating an approximately 500 nm-1 lm-thick metal- lic layer, as conducting substrate, onto one surface of the insulating template membrane by the sputter deposition technique. A two-compartment electro- chemical cell was designed and used for this work. The PC membrane was placed between the two compartments separating the aqueous solution of HAuCl4 from mercury. Mercury, filled in one of the compartments, is in contact with one surface of the membrane (similar to sputter-deposited metallic layer) and serves as the conducting substrate/cathode for the electrochemical deposition of gold in the nanopores of track-etched PC membrane. Once the electrodeposit- ion is completed, the mercury and the HAuCl4 solution are removed from the compartments, and a malleable track-etched PC membrane embedded with free-standing gold nanorods is obtained. The ensemble of the metal nanorods grown in the template membrane is not attached to any conducting substrate, and gold nanorods can be freed from the template membrane after the dissolution. The Au-deposited PC membrane and free- standing Au nanorods were characterized by EDXRF, XRD, UV-Visible spectroscopy, AFM, and FEG-TEM. The EDXRF and XRD studies confirmed the deposition of the face-centered cubic phase of Au in the pores of the PC membrane. The TEM studies showed the formation of a cigar-shaped gold nanorod in the cylindrical pores of the PC membrane. The diameter of gold nanorods ranges from 100 to 200 nm. The new approach is simple, cost- effective, and saves time.

Helix-Coiled Gold Nanowires for Molecular Sensing

Helix-coiled gold nanowires were fabricated by a templating route using unique composite templates consisting of anodic aluminum oxide (AAO) nanotubular membrane and confined mesoporous silica therein. A different degree of confinement energy induces a different degree of helix curvature of confined porous silica nanochannels in an AAO, which works as a hard template for the electrochemical deposition of gold, thereby rationally enabling a different degree of helix curvature of gold nano-replicas. From surface-enhanced Raman scattering experiments, we first found that helix-coiled gold nanowires show more distinctly enhanced molecule sensing efficiency than those from simple smooth gold nanowires, and gold nanowires with the narrower lateral width show more enhanced molecule sensing efficiency than those of thicker width helix nanowires.

Electrochemical deposition of gold at liquid–liquid interfaces studied by thin organic film-modified electrodes

The unique physico-chemical properties of gold nanoparticles portrayed in their chemical stability, the size-dependent electrochemistry, and the unusual optical properties make them suitable modifiers of various surfaces used in the fields of optical devices, electronics, and biosensors. In this work we present two different methods to obtain metallic gold nanoparticles at a liquid–liquid interface, and to control their growth by adjusting the experimental conditions. Decamethylferrocene (DMFC), used as an oxidizable compound dissolved in an organic solvent that is spread as a thin film on the surface of graphite electrode, serves as a redox partner to exchange electrons across the liquid–liquid interface with the other redox counter-partner [AuCl4]− present in the conjoined water phase. The interfacial electron transfer between the DMFC and the [AuCl4]− ions leads to deposition of metallic gold nanoparticles at the liquid–liquid interface. The structure and features of the deposited Au nanoparticles were studied by means of microscopic and voltammetric techniques. The morphology of the Au deposit depends on the concentration ratio of redox partners and both electrode and liquid–liquid interfacial potential differences. Depending on whether the Au deposit was obtained by ex situ (at open circuit potential) or by “in situ” (by cycling of the electrode potential) approach, we observed quite different effects to the ion transfer reactions probed by the thin-film electrode set-up. The possible reasons for the different behavior of the Au nanoparticles are discussed in terms of the structure and the properties of the obtained Au deposit. In separate experiments, we have demonstrated catalytic effects of the Au nanoparticles towards enhancing the electron transfer between DMFC and two aqueous redox substrates, hexacyanoferrate and hydrogen peroxide.

Engineering of Complex Macroporous Materials Through Controlled Electrodeposition in Colloidal Superstructures

AbstractMacroporous materials with a sophisticated architecture are obtained by electrochemical deposition of gold or polypyrrole in colloidal‐crystal templates. The Langmuir–Blodgett technique enables assembly of sub‐micrometric silica‐particle monolayers on conductive gold substrates, thus leading to colloidal superstructures with an unprecedented control of their features at the single‐bead‐layer level. This allows the integration of deliberate planar defects or the elaboration of well‐defined gradients in terms of sphere size. Controlled infiltration using electrochemical deposition preserves the architecture of the original templates and leads to inverse opals with well‐defined pore structures after the removal of the inorganic particles.

Highly Sensitive Detection of Exocytotic Dopamine Release Using a Gold-Nanoparticle-Network Microelectrode

Here we report a new type of microelectrode sensor for single-cell exocytotic dopamine release. The new microsensor is built by forming a gold-nanoparticle (AuNP) network on a carbon fiber microelectrode. First a gold surface is obtained on a carbon fiber microdisk electrode by partially etching away the carbon followed by electrochemical deposition of gold into the pore. The gold surface is chemically functionalized with a sol-gel silicate network derived from (3-mercaptopropyl)trimethoxysilane (MPTS). A AuNP network is formed by immobilizing Au nanoparticles onto the thiol groups in the sol-gel silicate network. The AuNP-network microelectrode has been characterized by scanning electron microscopy (SEM) and steady-state voltammetry. The AuNP-network microelectrode has been used for amperometric detection of exocytotic dopamine secretion from individual pheochromocytoma (PC12) cells. The results show significant differences in the kinetic peak parameters including shorter rise time, decay time, and half-width as compared to a bare carbon fiber electrode equivalent. These results indicate AuNP-network microelectrodes possess an excellent sensing activity for single-cell exocytotic catecholamine release, specifically dopamine. Moreover, key advantageous properties inherent to bare carbon fiber microelectrodes (i.e., rigidity, flexibility, and small size) are maintained in addition to an observed prolonged shelf life stability and resistance to cellular debris fouling and dopamine polymerization.

Design of Catalytically Active Cylindrical and Macroporous Gold Microelectrodes

AbstractPorous gold structures with a well‐defined pore size and thickness are obtained through electrochemical deposition of gold in a colloidal crystal template synthesized by the Langmuir–Blodgett (LB) technique. Cylindrical gold wires were used as substrates for the LB deposition of successive monolayers of silica particles of various sizes, and the electrodeposition of gold through this inorganic template led to a homogeneous, porous metal structure. These materials were characterized through typical electrochemical experiments and showed high surface‐to‐volume ratios with promising features for their further use in miniaturized electrocatalytic devices.

Electrodeposition of Au from [EMIm][TFSA] room-temperature ionic liquid: An electrochemical and Surface-Enhanced Raman Spectroscopy study

Abstract In this paper we report in situ Surface-Enhanced Raman Scattering (SERS) experiments carried out during the electrochemical deposition of gold from Au(I) cyanocomplexes in the room-temperature ionic liquid (RTIL) 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) amide ([EMIm][TFSA]). The obtained SERS spectra indicated the co-adsorption of CN − and both anions and cations of the RTIL in the range from −1.8 to +0.3 V vs. an Au quasi-reference electrode (QRE). The surface CN − peak exhibits a Stark tuning of ca. 28 cm −1 V −1 . The oxidation of CN − to OCN − was observed at potentials more anodic than 0.3 V. The study was complemented by cyclic voltammetry, pinpointing RTIL reactivity at an Au electrode as well as CN − adsorption effects and Au(I) reduction. SEM observations allowed to identify the conditions for the achievement of continuous Au films as well as the morphological peculiarities of Au electrodeposited from [EMIm][TFSA]. XPS measurements proved that no RTIL is incorporated into the Au film, under the investigated conditions.

Morphology, luminescence, and electrical resistance response to H 2 and CO gas exposure of porous InP membranes prepared by electrochemistry in a neutral electrolyte

Porous InP membranes have been prepared by anodization of InP wafers with electron concentration of 1 × 10 17 cm −3 and 1 × 10 18 cm −3 in a neutral NaCl electrolyte. The internal surfaces of pores in some membranes were modified by electrochemical deposition of gold in a pulsed voltage regime. Photoluminescence and photosensitivity measurements indicate efficient light trapping and porous surface passivation. The photoluminescence and electrical resistivity of the membranes are sensitive to the adsorption of H 2 and CO gas molecules. These properties are also influenced by the deposition of Au nanoparticles inside the pores.

Electrochemical deposition of gold–platinum alloy nanoparticles on an indium tin oxide electrode and their electrocatalytic applications

Gold–platinum (Au–Pt) hybrid nanoparticles (Au–PtNPs) were successfully deposited on an indium tin oxide (ITO) surface using a direct electrochemical method. The resulting nanoparticles were characterized by scanning electron microscopy (SEM), UV–vis spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and electrochemical methods. It was found that the size of the Au–PtNPs depends on the number of electrodeposition cycles. Au–PtNPs obtained by 20 electrodeposition cycles had a cauliflower-shaped structure with an average diameter of about 60 nm. These Au–PtNPs exhibited alloy properties. Electrochemical measurements showed that the charge transfer resistivity was significantly decreased for the Au–PtNPs/ITO electrode. Additionally, the Au–PtNPs displayed an electrocatalytic activity for nitrite oxidation and oxygen reduction. The Au–PtNPs/ITO electrodes reported herein could possibly be used as electrocatalysts and sensors.

Electrochemical Gold Deposition from Non-Toxic Electrolytes

An additive free electrolyte containing aurochloric acid, sodium sulphite and sodium thiosulphate has been used to electrodeposit gold. The electrolyte is stable at near neutral conditions and was stable on storage after formulation. Laboratory scale experiments showed that the electrolyte was compatible with positive photoresists. UV-Vis spectroscopy and cyclic voltammetry indicate that gold is discharged from a thiosulphate ligand. Industrial scale piloting experiments showed that high quality gold could be deposited from the electrolyte.

Gold–titania nanocomposite films with a periodic 3D nanostructure

In this study, we synthesized gold–titania nanocomposite thin films by using mesoporous titania thin films formed on indium tin oxide substrates as templates. The pore structure of our mesoporous titania thin films can be described as a periodic 3D pore network by interconnecting 7 nm sized cages. Electrochemical deposition of gold into the pores led to gold–titania nanocomposite films. Both gold and titania form continuous 3D network structures with internal periodicity. Because of the low conductivity of indium tin oxide substrate, the deposited gold formed isotropic islands. The absorption spectrum of the resultant gold–titania nanocomposite thin films showed two peaks, one at 640 nm and the other over a broad range of wavelengths longer than 1500 nm. These peaks grow with the increase of the deposition time but do not change the positions. The optical properties were explained in terms of the unique nanostructure of our gold–titania nanocomposite film.

Emission enhancement within gold spherical nanocavity arrays

Gold nanocavity arrays were prepared on fluorine-doped tin oxide on glass by electrochemical deposition of gold through monolayers of polystyrene spheres. The impact of the resulting spherical cap architecture on the photophysics of solutions and self-assembled monolayers of luminophore encapsulated within the nanocavities is reported for the first time. From conventional confocal fluorescence microscopy, the emission intensity of solutions of [Ru(bpy)(2)(Qbpy)](2+) (where bpy is 2,2'-bipyridyl and Qbpy is 2,2':4,4'':4,4''-quarterpyridyl) and fullerene (C(60)) encapsulated within the 820 nm diameter nanocavities was demonstrated to increase by approximately an order of magnitude compared with that of the associated bulk solution. Comparison was also made with the emission observed for luminophore solution encapsulated in cobalt nanocavities of comparable dimensions, where plasmonic interactions are not anticipated. Again, approximately an order of magnitude enhancement was observed for the gold arrays. Luminescence lifetime imaging revealed that the enhancement of the emission intensity of this solution within the nanocavity was accompanied by a small but significant decrease in the luminescent lifetime for [Ru(bpy)(2)(Qbpy)](2+). Enhancement was, in addition, strongly influenced by the wavelength of excitation, suggesting that plasmonics may play a role in the enhancement of the excitation process. An important observation from confocal imaging studies was that the dimensions of the luminophore emission field from solution within the cavities were significantly smaller than the dimensions of the cavity aperture and corresponded to a little more than that of the point spread function of the microscope. This indicates that its origin is significantly smaller than the wavelength of the emitted light and suggests that luminescence enhancement is highly localised. When the array was filled with a solution of [Ru(bpy)(2)(Qbpy)](2+) the emission spectrum of this complex was red shifted and broadened compared with that of the bulk solution, typical of the formation of a luminescent surface film. In addition, significant enhancement was only observed when the solution was sonicated into the array. Both these observations suggest that the emission enhancement is localised near the bottom of the cavity. Self-assembled monolayers of [Ru(bpy)(2)(Qbpy)](2+) were formed on the array and approximately 7 orders of magnitude enhancement of the Raman signal was achieved. Significantly, the emission intensity was approximately 4-fold higher for the monolayer than for a solid film under the same conditions, but surface quenching is thought to play a significant role in the observed decrease in lifetime for the monolayer of this complex on the array.

Electrochemical Gold Deposition from Non-Toxic Electrolytes

not Available.

Selective electrochemical gold deposition onto p-Si (1 0 0) surfaces

In this paper, we report selective electrochemical gold deposition onto p-type Si (1 0 0) into nanoscratches produced through a thin oxide layer using an atomic force microscope. A detailed description of the substrate engraving process is presented. The influence of the main scratching parameters such as the normal applied force, the number of scans and the scanning velocity are investigated as well as the mechanical properties of the substrate. Gold deposition is carried out in a KAu(CN)2 + KCN solution by applying cathodic voltages for various durations. The gold deposition process is investigated by cyclic voltammetry. Reactivity enhancement at the scratched locations was studied by comparing the electrochemical behaviour of intact and engraved surfaces using a micro-electrochemical setup. Selective electrochemical gold deposition is achieved: metallic patterns with a sub-500 nm lateral resolution are obtained demonstrating, therefore, the bearing potential of this patterning technique.

Ordered macroporous gold thin film with encaptured polymer spheres

A two-dimensional colloidal crystal fabricated from core-shell polystyrene spheres was employed as a template for the electrochemical deposition of gold. By partially embedding the colloidal spheres into the gold film and selectively removing the shells of the colloidal spheres, highly ordered macroporous gold thin films with captured polystyrene spheres were obtained.

Enzyme-free glucose sensor based on a three-dimensional gold film electrode

Abstract An enzyme-free glucose sensor has been developed using a three-dimensional inverse-opal gold film electrode (3DGFE) obtained by electrochemical deposition of gold in the interspaces of polystyrene templates. The gold films were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The electrochemical oxidation of glucose in the presence of interferents (ascorbic acid, and so on) at different operating potentials on the 3DGFE has been investigated in detail. A low operating potential of −0.30 V was chosen for glucose detection, since the interference could be well avoided at this potential, whereas the current response for glucose oxidation was still sensitive. The amperometric response of the sensor increased with the increase of glucose concentration with a linear range of 5 × 10−6 to 10−2 M and a detection limit of 3.2 μM (signal-to-noise ratio of 3). The glucose sensor exhibited a high sensitivity of 46.6 μA mM−1 cm−2, which could be ascribed to the unique surface structure of the three-dimensionally interconnected porous structured gold films. The sensor with high sensitivity, good selectivity and stability is attractive for the practical glucose detection.

Electrochemical gold deposition from sulfite solution: application for subsequent polyaniline layer formation

Electrochemical gold deposition from sulfite solutions was studied by means of voltammetry, EIS and EQCM. A gold film electrode was used for polyaniline layer formation by electrochemical oxidation of aniline. The standard electrochemical reduction potential of the reaction (Au(SO3)2) 3- + e - = Au + 2S O 3- was deter- mined, and is equal to 0.116 V (vs. NHE). Both solution stirring and temperature increase accelerate the electro- chemical reduction of gold, when the electrode potential is below -0.55 V. When the potential is above -0.55 V the electrochemical reduction proceeds via passive layer for- mation. Our study suggests that the passive layer consists of chemically adsorbed sulfite ions and sulfur. The gold film deposited from sulfite solution is a high quality sub- strate suitable for conducting polymer layer formation. This technique, where a polymer layer electrode is pre- pared by thin gold film deposition onto a metal surface and by subsequent polymer layer formation, can be applied in sensor research and technology.