Electrochemical Deposition Of Gold Research Articles

Specific features of epitope-MIPs and whole-protein MIPs as illustrated for AFP and RBD of SARS-CoV-2.

Molecularly imprinted polymer (MIP) nanofilms for alpha-fetoprotein (AFP) and the receptor binding domain (RBD) of the spike protein of SARS-CoV-2 using either a peptide (epitope-MIP) or the whole protein (protein-MIP) as the template were prepared by electropolymerization of scopoletin. Conducting atomic force microscopy revealed after template removal and electrochemical deposition of gold a larger surface density of imprinted cavities for the epitope-imprinted polymers than when using the whole protein as template. However, comparable affinities towards the respective target protein (AFP and RBD) were obtained for both types of MIPs as expressed by the KD values in the lower nanomolar range. On the other hand, while the cross reactivity of both protein-MIPs towards human serum albumin (HSA) amounts to around 50% in the saturation region, the nonspecific binding to the respective epitope-MIPs is as low as that for the non-imprinted polymer (NIP). This effect might be caused by the different sizes of the imprinted cavities. Thus, in addition to the lower costs the reduced nonspecific binding is an advantage of epitope-imprinted polymers for the recognition of proteins.

Improvement of Low-Cost Commercial Carbon Screen-Printed Electrodes Conductivities with Controlled Gold Reduction Towards Thiol Modification

Effectively detecting bacteria in the environment is crucial for researchers to make informed decisions about the safety of public areas, such as lakes. This led to an increased need in the development of portable handheld devices, capable of on-the-spot chemical and biological sensing applications. Specific interests lie in electrochemical biosensors and screen-printed electrodes (SPEs) due to the decreased costs, an ability to integrate with handheld devices, and their user-friendly nature. Together, these qualities make the devices more accessible in resource-poor settings. Two of the most common substrates used to fabricate SPEs are carbon and gold. Carbon SPEs are effective in sensing applications yet challenged when attempting to covalently attach biomolecules to the surface. Gold SPEs have higher affinity towards biomolecules and improve the sensitivity, selectivity, and stability of a device; yet they can be costly. A carbon SPE modified with gold may be an ideal candidate to create an efficient low-cost device, using electrochemical gold deposition. In this study, electrochemical gold deposition on SPEs is explored to enhance the surface area and conductivity towards sensing applications. These SPEs were then modified with a thiol-based self-assembled monolayer (SAM) which demonstrates this technique could be used for further modification towards biosensing.

Fabrication of electron tunneling probes for measuring single-protein conductance.

Studying the electrical properties of individual proteins is a prominent research area in the field of bioelectronics. Electron tunnelling or quantum mechanical tunnelling (QMT) probes can act as powerful tools for investigating the electrical properties of proteins. However, current fabrication methods for these probes often have limited reproducibility, unreliable contact or inadequate binding of proteins onto the electrodes, so better solutions are required. Here, we detail a generalizable and straightforward set of instructions for fabricating simple, nanopipette-based, tunnelling probes, suitable for measuring conductance in single proteins. Our QMT probe is based on a high-aspect-ratio dual-channel nanopipette that integrates a pair of gold tunneling electrodes with a gap of less than 5 nm, fabricated via the pyrolytic deposition of carbon followed by the electrochemical deposition of gold. The gold tunneling electrodes can be functionalized using an extensive library of available surface modifications to achieve single-protein-electrode contact. We use a biotinylated thiol modification, in which a biotin-streptavidin-biotin bridge is used to form the single-protein junction. The resulting protein-coupled QMT probes enable the stable electrical measurement of the same single protein in solution for up to several hours. We also describe the analysis method used to interpret time-dependent single-protein conductance measurements, which can provide essential information for understanding electron transport and exploring protein dynamics. The total time required to complete the protocol is ~33 h and it can be carried out by users trained in less than 24 h.

Voltammetric Quantification of the Antibiotic Roxarsone using a Surface‐Modified Screen‐Printed Carbon Electrode

AbstractHerein, we report the electrochemical determination of roxarsone (ROX) on modified screen‐printed carbon electrodes (SPCE). Graphene oxide was reduced electrochemically on the working area of SPCE using cyclic voltammetry (CV) to form electrochemically reduced graphene oxide (ErGO), followed by electrochemical deposition of gold (Au) on ErGO/SPCE to get a final modified electrode Au/ErGO/SPCE. The modified electrode offered a significant surface area and improved electron transfer capability; hence it was used as an electrochemical sensor for the determination of ROX which is commonly used in meat production and poultry as a supplement to increase weight and improve feed efficiency. The effect of pH on the electrochemical behaviour of ROX on the Au/ErGO/SPCE was investigated by (CV) and square wave voltammetry (SWV). Under optimum experimental conditions, the linear calibration range, the limit of detection (LOD), and quantification (LOQ) were found to be 1 μmol L−1–1000 μmol L−1, 14.4 nmol L−1, and 47.9 nmol L−1 respectively. The proposed electrochemical sensor was successfully applied to determine low concentrations of ROX in lab samples as well as in real meat (spiked) samples. Overall, a good recovery rate and accuracy were obtained, endorsing onsite use of the developed sensor for quick and accurate analysis.

Hierarchical Structure of Gold and Carbon Electrode for Bilirubin Oxidase-Biocathode.

Biofuel cells (BFCs) with enzymatic electrocatalysts have attracted significant attention, especially as power sources for wearable and implantable devices; however, the applications of BFCs are limited owing to the limited O2 supply. This can be addressed by using air-diffusion-type bilirubin oxidase (BOD) cathodes, and thus the further development of the hierarchical structure of porous electrodes with highly effective specific surface areas is critical. In this study, a porous layer of gold is deposited over magnesium-oxide-templated carbon (MgOC) to form BOD-based biocathodes for the oxygen reduction reaction (ORR). Porous gold structures are constructed via electrochemical deposition of gold via dynamic hydrogen bubble templating (DHBT). Hydrogen bubbles used as a template and controlled by the Coulomb number yield a porous gold structure during the electrochemical deposition process. The current density of the ORR catalyzed by BOD without a redox mediator on the gold-modified MgOC electrode was 1.3 times higher than that of the ORR on the MgOC electrode. Furthermore, the gold-deposited electrodes were modified with aromatic thiols containing negatively charged functional groups to improve the orientation of BOD on the electrode surface to facilitate efficient electron transfer at the heterogeneous surface, thereby achieving an ORR current of 12 mA cm-2 at pH 5 and 25 °C. These results suggest that DHBT is an efficient method for the fabrication of nanostructured electrodes that promote direct electron transfer with oxidoreductase enzymes.

Investigating electrochemical deposition of gold on commercial off-the-shelf 3-D printing materials towards developing sensing applications.

The COVID-19 pandemic highlighted the inaccessibility of quick and affordable clinical diagnostics. This led to increased interest in creating low-cost portable electrochemical (EC) devices for environmental monitoring and clinical diagnostics. One important perspective is to develop new fabrication methods for functional and low-cost electrode chips. Techniques, such as electron beam and photolithography, allow precise and high-resolution electrode fabrication; however, they are costly and can be time-consuming. More recently, fused deposition modeling three-dimensional (3-D) printing is being used as an alternative fabrication technique due to the low-cost of the printer and rapid prototyping capability. In this study, we explore enhancing the conductivity of 3-D printed working electrodes with EC gold deposition. Two commercial conductive filament brands were used and investigated to fabricate electrode chips. Furthermore, strategies to apply epoxy glue and conductive silver paint were investigated to control the electrode surface area and ensure good electrical connection. This device enables detection at drinking water concentration thresholds. The practical application of the fabricated electrodes is demonstrated by detecting Cu2+ using anodic stripping voltammetry.

Comparative Study of the Processes of Electrochemical Deposition of Gold From Cyanide and Sulphite-Thiosulphate Electrolytes

Comparative Study of the Processes of Electrochemical Deposition of Gold From Cyanide and Sulphite-Thiosulphate Electrolytes

Evidence supporting micro-galvanic coupling in sulphides leads to gold deposition

Electrical micro-junctions in metal sulfides drive electrochemical reactions with passing gold-bearing fluids, resulting in the deposition of gold, even from under-saturated ore fluids. Understanding the role micro-junctions play in the deposition of gold requires (a) imaging the electric field distribution of a galvanic couple near the surface to qualify the existence of an active micro-geo-battery and (b) correlating it with gold precipitation on the p-type cathode side of the junction by mapping the host at minor and trace levels. Here we report on correlating electron back scattered diffraction (EBSD), particle induced X-ray emission (PIXE) elemental maps including micron-scaled gold hot spots with laser beam induced current (LBIC) photocurrent maps of galvanic coupling in natural arsenian pyrite from the Otago Schist in New Zealand. The results provide convincing evidence that sulphide electrochemical interactions can lead to gold electro-deposition. We finish by discussing a simplistic model of the processes involved in reference to the original model of Moller and Kersten (Miner Deposita 29(5):404–413. 1994), and discuss the effects of temperature in light of recent-reported evidence of electrochemical gold deposition in the formation of hydrothermal gold deposits.

Electrochemical deposition of gold nanoparticles‐based plasmonic catalyst for glucose oxidation

AbstractThis work describes an effective electrodeposition method for generating gold plasmonic electrodes which are further used for detecting glucose in solution without the presence of any enzymes (i.e Gox). Under light irradiation, the electro‐catalytic oxidation of glucose on the electrodeposited gold nanoparticle (AuNP) surfaces has been investigated. The wavelength‐dependent electrochemical oxidative current intensity implies that the hot carriers transferred from the excited plasmonic AuNPs to the absorbed molecules are responsible for enhancing electro‐catalysis performance. Hot holes can particularly contribute to the oxidation reaction of glucose on the plasmonic surfaces without the presence of any enzymes in solution. Furthermore, the presence of nano‐sized gold particles exhibits a larger active surface area, which leads to a significant improvement in recorded oxidative current for the oxidation of glucose. These results reveal a promising manner for generating non‐enzymatic glucose electrochemical sensor upon plasmonic excitation.

Hollow waveguide array with subwavelength dimensions as a space-variant polarization converter

A hollow waveguide array with subwavelength dimensions is demonstrated as a polarization converter. An individual waveguide in the array has a rectangular cross-section, which leads to an anisotropy of propagation constants and therefore to a phase shift between vertical and horizontal field components upon propagation. The hollow waveguide array was fabricated by a two-photon polymerization process followed by electrochemical deposition of gold. The fabricated array consists of about 2000×2500 hollow waveguide cells, each with dimensions of 1150 nm×930 nm and height of 2 μm. With these dimensions, the structure can, for example, be used at a wavelength of 1550 nm. Other wavelengths and phase shifts are accessible by changing the dimensions of the cross-section and the height. Since the widths of individual waveguides are variable, space-variant operation can be implemented.

Directing Nanostructure Formation of Gold through the In Situ Underpotential Deposition of a Secondary Metal for the Detection of Nitrite Ions

AbstractIn this work, the underpotential deposition of metals such as copper and lead during the electrochemical deposition of gold is investigated to understand the influence that the incorporation of a second metal has on the morphology of gold nanostructures. The incorporation of Pb or Cu, even at concentrations as low as 0.2 %, significantly influences the morphology of the deposit, where the formation of elongated structures from a central gold structure is favored. These nanostructures are characterized by cyclic voltammetry, X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy and are tested for their suitability as a sensing layer for the electrochemical detection of nitrite ions in aqueous solution. A limit of detection of 0.3 μM is achieved with a linear range up to 1 mM, which is adequate for the determination of nitrite contained within food products.

Nanomolar electrochemical detection of caffeic acid in fortified wine samples based on gold/palladium nanoparticles decorated graphene flakes

Amalgamation of noble metal nanomaterials on graphene flakes potentially paves one way to improve their physicochemical properties. This paper deals with the simultaneous electrochemical deposition of gold and palladium nanoparticles on graphene flakes (Au/PdNPs-GRF) for the sensitive determination of caffeic acid (CA). The physiochemical properties of the prepared Au/PdNPs-GRF was characterized by using numerous analytical techniques such as scanning electron microscopy, electron dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy and electrochemical impedance spectroscopy. The enhanced electrochemical determination of CA at Au/PdNPs deposition on GRF were studied by using cyclic voltammetry and differential pulse voltammetry. In results, Au/PdNPs-GRF electrode exhibited an excellent electrocatalytic activity towards CA with wide linear range and low limit of detection of 0.03–938.97µM and 6nM, respectively. Eventually, the Au/PdNPs-GRF was found as a selective and stable active material for the sensing of CA. In addition, the proposed sensor showed the adequate results in real sample analysis.

Electrodeposition of Gold on Lignocelluloses and Graphite-Based Composite Paper Electrodes for Superior Electrical Properties

Graphite-based composites are commonly used as an anode and current collector for energy storage devices; however, they have inherently limited potential for large scale rechargeable systems due to a brittle structure. In this study, flexible and light-weight graphite-based electrodes are prepared by incorporation of lignocelluloses fibers directly collected from a self-growing plant, Typha Angistifolia. Electrical properties of graphite and lignocelluloses composite sheets are enhanced by electrodeposition of gold in a three-electrode setup. Electrochemical deposition of gold on a lignocelluloses/graphite paper electrode was obtained in potentiostatic mode by the application of reduction potential −0.95 V for 2000 s, 600 s, and 100 s. The gold-deposited paper electrodes showed efficient kinetics by shifting redox peaks towards lower potentials in cyclic voltammetry measurements, whereas impedance measurements revealed seven orders of magnitude reduction in the resistive properties. Incorporated flexibility and superior electrical/electrochemical performance within presented graphite-based composites will provide cutting-edge characteristics for high-tech application of energy storage devices by keeping a focus on modern disposable technology.

Formation of alloys upon the simultaneous electrochemical deposition of gold and tin from ethylene glycol and aqueous electrolytes

An ethylene glycol (EG) solution containing Au(III) and Sn(IV) compounds, and conditions for the electrochemical deposition of Au–Sn alloy based on AuSn and Au5Sn intermetallics with total tin content of 30–55 at % are proposed. Fundamental difficulties of the deposition of alloys with high tin content, (including eutectic Au–Sn alloy) from aqueous electrolytes are revealed. It is determined via voltammetry that the simultaneous deposition of gold and tin from aqueous and EG electrolytes proceeds with the depolarization effect of both Au(III) and Sn(IV) as a result of the formation of the alloy, the increase in the rate of tin cathodic reduction being more noticeable in case of EG solution. Formation of SnCl2EG(H2O)2+ complex upon the dissolution of SnCl4 · 5H2O in glycol, the stability of the composition of tetracyanoaurate ions upon the dissolution of K[Au(CN)4], and the weakening of intermolecular interactions in EG with small amounts of water were revealed via IR spectroscopy. It is suggested that the depolarization effect is due not only to alloy formation, but also to the formation of SnCl2EG(H2O)2+ cations, their association with Au(CN)4- anions, and a change in the mechanism of Au(III) and Sn(IV) reduction.

Rough Gold Electrodes for Decreasing Impedance at the Electrolyte/Electrode Interface

Electrode polarization at the electrolyte/electrode interface is often undesirable for bio-sensing applications, where charge accumulated over an electrode at constant potential causes large potential drop at the interface and low measurement sensitivity. In this study, novel rough electrodes were developed for decreasing electrical impedance at the interface. The electrodes were fabricated using electrochemical deposition of gold and sintering of gold nanoparticles. The performances of the gold electrodes were compared with platinum black electrodes. A constant phase element model was used to describe the interfacial impedance. Hundred folds of decrease in interfacial impedance were observed for fractal gold electrodes and platinum black. Biotoxicity, contact angle, and surface morphology of the electrodes were investigated. Relatively low toxicity and hydrophilic nature of the fractal and granulated gold electrodes make them suitable for bioimpedance and cell electromanipulation studies compared to platinum black electrodes which are both hydrophobic and toxic.

Synergetic Light-Harvesting and Near-Field Enhancement in Multiscale Patterned Gold Substrates

Sphere-segment void (SSV) cavities have emerged as promising substrates for reproducible Surface Enhanced Raman Scattering (SERS), offering strong and uniform electromagnetic enhancement associated with the excitation of cavity-like localized surface plasmon resonances tunable across the UV–vis-near IR range, with a facile large-scale fabrication process. High-resolution electron micrographs of these structures reveal a considerable departure from the idealized smooth spherical cavity shape; notably, the electrochemical deposition of gold yields an important surface roughness. We investigate this contribution to the SERS activity of SSV substrates with a series of experiments, varying the degree of surface roughness using thermal annealing and gradual electrochemical roughening. Notably, we observe that both roughness features and cavity-like modes operate in conjunction as a multiscale antenna to provide larger SERS efficiency than the two mechanisms considered separately. We conclude that the main role ...

A Helical Metamaterial for Broadband Circular Polarization Conversion

Metallic helical metamaterials give rise to broadband and scalable chiro‐optical effects orders of magnitude higher than found in nature. While arrays of gold helices have been suggested as compact circular polarizers, where a large difference of the diagonal elements of the Jones transmission matrix is desired, chiral metamaterials can also be designed to exhibit strong circular‐polarization conversions. Here, a novel helical metamaterial design, exhibiting asymmetric, broadband circular‐polarization conversion, is introduced. The metamaterial is composed of unit cells with a single helix that changes its handedness halfway along the helix axis. Based on numerical calculations, an intuitive model explaining the principle of operation is given. Furthermore, a novel fabrication approach employing STED‐inspired direct laser writing in combination with electrochemical deposition of gold is presented. The experimental data show circular‐polarization conversion of up to 75% for an unmatched bandwidth of one octave, in very good agreement with theory.

Electrochemical deposition of gold on indium zirconate (InZrOx with In/Zr atomic ratio 1.0) for high temperature automobile exhaust gas sensors

Automobile exhaust gas emissions are causing serious damage to urban air quality in and around major cities of the world, which demands continuous monitoring of exhaust emissions. The chief components of automobile exhaust include carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons. Indium zirconate (InZrOx) and gold/indium zirconate (Au/InZrOx) composite nanopowders are believed to be interesting materials to detect these substances. To this end, characterization and gas sensing properties of InZrOx and Au/InZrOx composite nanopowders are discussed. InZrOx nanoparticles with In/Zr atomic ratio of 1.00 (±0.05) are synthesized via pH-controlled co-precipitation of In and Zr salts in aqueous ammonia. Gold (Au) nanoparticles are subsequently deposited on InZrOx using an in situ sacrificial Au electrolysis procedure. The products are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing performance of Au/InZrOx composite nanopowder is studied by depositing a thick powder film on interdigitated electrode structures patterned on SiC substrate to facilitate high temperature operation. The resistivity of the Au/InZrOx layer is the sensor signal, and the sensors could be operated at 500–600 °C, which is a suitable temperature range for engine exhaust measurements. The control sensing measurements reveal that Au/InZrOx composite nanopowder exhibits higher response towards 2–20 % O2 gas as compared to pristine InZrOx nanoparticles. Further studies show that when applied to exhaust gases such as CO and nitric oxide (NO), the response of Au/InZrOx sensors is significantly higher towards NO in this temperature range. Thus, sensor performance characteristics of Au/InZrOx composite nanopowder are promising in terms of their applications in automobile exhaust emission control.

Capacitor with an electrode based on nanostructured gold

The method for generating a supercapacitor based on nanostructured gold is proposed; the special features of this supercapacitor are described. The process of electrochemical deposition of gold is elaborated. By using a scanning electron microscope, the morphology of the obtained deposits is studied. The optimal conditions for enlarging the capacitance are defined. It is shown that with the use of a nanostructured layer of gold the capacitance of relatively planar electrodes can be enlarged by a factor of 106.

Electrogeneration of hydrogen peroxide for electro-Fenton system by oxygen reduction using gold nanoparticle electrodeposited on graphite cathode

In this study, the electrochemical deposition of gold (Au) onto graphite has been performed under different deposition potential conditions. These Au particles electrodeposited on the graphite were used as cathode for O2 electrochemical reduction and H2O2 production in acidic solution, and the hydrogen peroxide (H2O2) electrogenerated on graphite modified by gold particles was used in electro-Fenton process. Results show firstly that the O2 cathodic reduction on gold particles electrodeposited on the graphite electrode in acidic medium with two well-defined reduction waves at −300 mV/SCE and −1,300 mV/SCE; those waves indicated reduction of two O2 electrons to H2O2. Secondly, the optimal cathodic potential condition for H2O2 generation on cathode modified was −300 mV and unmodified one was −500 mV/SCE. The electrolysis time, dissolved oxygen level, magnetic stirring, and pH were systematically studied; the hydrogen peroxide production increased with the aeration and electrolysis time and then became stationary after 2 h of electrolysis. The maximum H2O2 accumulation increased up to 60 mg/L with air compressed, at −300 mV. Optimized parameters (potential, oxygen level, and concentration of ferrous ions) were also applied to incinerate the Belgard EV2030 sodium salt of polycarboxylic acid. The incineration efficiency onto optimized parameters shows that 74% of Chemical oxygen demand was incinerated in the modified electrode that confirms the positive gold modification effect onto the performance.