Bare Gold Research Articles

Effect of concentration of PEG coated gold nanoparticle on lung surfactant studied with coarse-grained molecular dynamics simulations

The surface modification of nanoparticles can not only change the physical and chemical properties of particles, such as the hydrophilic and hydrophobic properties and surface charges of nanoparticles to a certain extent, but also bring new functions to nanoparticles, such as membrane permeability and targeting. Inhaled nanoparticles (NPs) are experienced by the first biological barrier inside the alveolus known as lung surfactant (LS), consisting of phospholipids and proteins in the form of the monolayer at the air-water interface. Inhaled NPs can reach deep into the lungs and interfere with the biophysical properties of the lung components. The interaction mechanisms of bare gold nanoparticles (AuNPs) with the LS monolayer are not well understood. Coarse-grained molecular dynamics simulations were carried out to have a study on the interactions of PEG coated AuNPs with LS monolayers. It was observed that the interactions of AuNPs and LS components make the monolayer structure deform and change the biophysical properties of LS monolayer. The results also indicate that AuNPs with high concentrations hinder the lowering of the LS surface tension and reduce lateral mobility of lipids. Overall, the simulation results can provide guidance for the design of ligand protected NPs as drug carriers and can identify the nanoparticles potential side effect on lung surfactant.

Nb.BbvCI powered DNA walking machine-based Zr-MOFs-labeled electrochemical aptasensor using Pt@AuNRs/Fe-MOFs/PEI-rGO as electrode modification material for patulin detection

A Nb.BbvCI powered DNA walking machine as signal enhancer, gold-platinum core-shell nanorods/iron-based metal-organic frameworks/polyethyleneimine-reduced graphene oxide composites (Pt@AuNRs/Fe-MOFs/PEI-rGO) as electrode modification material and Zr-based metal-organic frameworks-labeled oligonucleotides load with methylene blue (MB@Zr-MOFs-cDNA) as signal probes has been fabricated to obtain a sensitive electrochemical aptasensor for patulin (PAT) detection. In the DNA walking machine, PAT takes the aptamer away from the DNA walking chain (wDNA), and wDNA can repeatedly dissociate the MB@Zr-MOFs-cDNA under the Nb.BbvCI power to amplify the detection signal. In addition, Pt@AuNRs/Fe-MOFs/PEI-rGO modified gold electrode provides high stability (60 scans without significant change), catalytic performance (compared to bare gold electrode signal enhancement 250%), and high conductivity (calculated apparent electron transfer rate constant is 1.64 s−1). With such design, the as- prepared aptasensor exhibits good sensitivity from 5.0 × 10−5 ng·mL−1 to 5.0 × 10−1 ng·mL−1 with a detection limit of 4.14 × 10−5 ng·mL−1. This aptasensor construction mode can supply one efficient approach to improve signal amplification, which also open an avenue for sensitivity enhancement in detection of analytes.

Gold nanoclusters decorated amine-functionalized graphene oxide nanosheets for capture, oxidative stress, and photothermal destruction of bacteria

Gold nanoclusters decorated amine-functionalized graphene oxide (Au-GO-NH2) nanosheets were designed as a highly efficient visible light active antibacterial agent. This assembled nanosheet is positively charged and of high specific surface area that captures bacteria through physical adsorption and electrostatic interaction. Under visible light irradiation, this photoactive nanosheet concurrently generates massive heat and produces substantial reactive oxygen species to inactivate bacteria. In comparison with bare gold nanoclusters and amine-functionalized graphene oxides, this nanosheet appears an enhanced antibacterial activity >5-fold towards Gram-postive and Gram-negative bacteria. Moreover, a nanosheet modified silicone surface was employed as a model of implant devices, which showed superior antibacterial efficacy against bacterial colonization in vitro. This work demonstrates that the assembled nanosheet is a promising novel strategy in the construction of next generation antimicrobial agent for synergistic bacterial capture, oxidative stress, and photothermal ablation in the biomedical and environmental fields.

Stellate Plasmonic Exosomes for Penetrative Targeting Tumor NIR-II Thermo-Radiotherapy.

Multifunctional gold (Au)-based nanomaterials with high atomic number (symbol Z) and strong absorbance in the second near-infrared window (NIR-II) property are emerging as promising candidates for tumor thermo-radiotherapy. The main limitations of applying Au-based nanomaterials to biomedical studies include the absence of active tumor-targeting ability, penetrating efficiency, and stability. In this study, we present a novel type of tumor cell-derived stellate plasmonic exosomes (TDSP-Exos) for penetrative targeted tumor NIR-II thermo-radiotherapy and photoacoustic imaging. The TDSP-Exos are abundantly and easily produced by the incubation of tumor cells with gold nanostars, based on which gold nanostars promote the exocytosis of exosomes from tumor cells. Compared with bare gold nanostars, the TDSP-Exos exhibit pronounced accumulation in deep tumor tissues and perform well in both PA imaging and NIR-II thermo-radiotherapy against the tumor. Moreover, the TDSP-Exos improve tumor hypoxia to enhanced radiotherapy by NIR-II photothermal therapy. This work indicates that the tumor cell-derived exosomes have the potential to function as a universal carrier of photothermal agents for targeted tumor NIR-II thermo-radiotherapy.

Enhancement of the Start-Up Time for Microliter-Scale Microbial Fuel Cells (µMFCs) via the Surface Modification of Gold Electrodes.

Microbial Fuel Cells (MFCs) are biological fuel cells based on the oxidation of fuels by electrogenic bacteria to generate an electric current in electrochemical cells. There are several methods that can be employed to improve their performance. In this study, the effects of gold surface modification with different thiol molecules were investigated for their implementation as anode electrodes in micro-scale MFCs (µMFCs). Several double-chamber µMFCs with 10.4 µL anode and cathode chambers were fabricated using silicon-microelectromechanical systems (MEMS) fabrication technology. µMFC systems assembled with modified gold anodes were operated under anaerobic conditions with the continuous feeding of anolyte and catholyte to compare the effect of different thiol molecules on the biofilm formation of Shewanella oneidensis MR-1. Performances were evaluated using polarization curves, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microcopy (SEM). The results showed that µMFCs modified with thiol self-assembled monolayers (SAMs) (cysteamine and 11-MUA) resulted in more than a 50% reduction in start-up times due to better bacterial attachment on the anode surface. Both 11-MUA and cysteamine modifications resulted in dense biofilms, as observed in SEM images. The power output was found to be similar in cysteamine-modified and bare gold µMFCs. The power and current densities obtained in this study were comparable to those reported in similar studies in the literature.

Integrated Glycosylation Patterns of Glycoproteins and DNA Methylation Landscapes in Mammalian Oogenesis and Preimplantation Embryo Development.

Glycosylation is one of the most fundamental post-translational modifications. However, the glycosylation patterns of glycoproteins have not been analyzed in mammalian preimplantation embryos, because of technical difficulties and scarcity of the required materials. Using high-throughput lectin microarrays of low-input cells and electrochemical techniques, an integration analysis of the DNA methylation and glycosylation landscapes of mammal oogenesis and preimplantation embryo development was performed. Highly noticeable changes occurred in the level of protein glycosylation during these events. Further analysis identified several stage-specific lectins including LEL, MNA-M, and MAL I. It was later confirmed that LEL was involved in mammalian oogenesis and preimplantation embryogenesis, and might be a marker of FGSC differentiation. Modified nanocomposite polyaniline/AuNPs were characterized by electron microscopy and modification on bare gold electrodes using layer-by-layer assembly technology. These nanoparticles were further subjected to accuracy measurements by analyzing the protein level of ten-eleven translocation protein (TET), which is an important enzyme in DNA demethylation that is regulated by O-glycosylation. Subsequent results showed that the variations in the glycosylation patterns of glycoproteins were opposite to those of the TET levels. Moreover, analysis of correlation between the changes in glyco-gene expression and female germline stem cell glycosylation profiles indicated that glycosylation was related to DNA methylation. Subsequent integration analysis showed that the trend in the variations of glycosylation patterns of glycoproteins was similar to that of DNA methylation and opposite to that of the TET protein levels during female germ cell and preimplantation embryo development. Our findings provide insight into the complex molecular mechanisms that regulate human embryo development, and a foundation for further elucidation of early embryonic development and informed reproductive medicine.

Electrochemical Study of Gold Microelectrodes Modified with PEDOT to Quantify Uric Acid in Milk Samples

AbstractA gold microelectrode (10 μm diameter) with an electropolymerized layer of poly(3,4‐ethylenedioxythiophene) (PEDOT) was used to quantify uric acid and investigate the antioxidant profile of milk and flavored milks. Comparisons were made with a bare gold microelectrode and a PEDOT‐glassy carbon macroelectrode (3 mm diameter). Two different electropolymerization processes were undertaken in an aqueous and an organic solution, and superior polymer growth was observed for PEDOT polymerized in lithium perchlorate/propylene carbonate. In the presence of a ferri/ferrocyanide redox couple, diffusion‐controlled redox peaks were observed with the PEDOT‐gold microelectrode rather than the plateau current typical of a bare microelectrode. Likewise, an anodic peak for uric acid was observed at the high surface‐area PEDOT‐gold microelectrode, with evidence for pre‐adsorption of uric acid at the electrode. The linear concentration range for uric acid standards was from 6 to 200 μM, and the limit of detection, limit of quantification, and sensitivity were determined to be 7 μM, 24 μM, and 397 μAμM−1cm2, respectively. Cyclic voltammograms of chocolate and espresso flavored milks exhibited significant contributions from the phenolic compounds present. Peak separation was more clearly defined using the PEDOT‐microelectrode compared to a PEDOT‐glassy carbon macroelectrode.

Optimization the Optical Structure of the NICA Collider

The optimization of the optical structure of the NICA Collider is presented. The Collider optics settings are given for a working point of 9.44/9.44 and a bare gold nuclei beam with energies of 1, 3, and 4.5 GeV/u. The dynamic aperture simulation and optimization results are given. The tolerance of the magnetic field errors for the Collider structural elements and the closed orbit adjustment precision are discussed.

Nanotunnels within Poly(3,4-ethylenedioxythiophene)-Carbon Nanotube Composite for Highly Sensitive Neural Interfacing.

Neural electrodes are developed for direct communication with neural tissues for theranostics. Although various strategies have been employed to improve performance, creating an intimate electrode-tissue interface with high electrical fidelity remains a great challenge. Here, we report the rational design of a tunnel-like electrode coating comprising poly(3,4-ethylenedioxythiophene) (PEDOT) and carbon nanotubes (CNTs) for highly sensitive neural recording. The coated electrode shows a 50-fold reduction in electrochemical impedance at the biologically relevant frequency of 1 kHz, compared to the bare gold electrode. The incorporation of CNT significantly reinforces the nanotunnel structure and improves coating adhesion by ∼1.5 fold. In vitro primary neuron culture confirms an intimate contact between neurons and the PEDOT-CNT nanotunnel. During acute in vivo nerve recording, the coated electrode enables the capture of high-fidelity neural signals with low susceptibility to electrical noise and reveals the potential for precisely decoding sensory information through mechanical and thermal stimulation. These findings indicate that the PEDOT-CNT nanotunnel composite serves as an active interfacing material for neural electrodes, contributing to neural prosthesis and brain-machine interface.

Development of oil-in-water microemulsion encapsulating Vitamin E for thermal and hydrolysis degradation study

Vitamin E is widely used for medicinal and cosmeceuticals purposes. However, it is easy to degrade by the environment. In this study, the degradation of Gold Tri.E™ was studied and determined. Gold Tri.E™ is a mixture of Vitamin E homologs (tocotrienol and tocopherol) extracted from palm oil (Elais Guineensis). A nanocarrier system has been optimized to encapsulate Gold Tri.E™ from degrading and increasing its stability as a bioactive compound. An oil-in-water (o/w) microemulsion was formulated and optimized as the best carrier to encapsulate Gold Tri.E™ with the mean particle size of 32.60±3.60 nm and 99.99±0.01% encapsulation efficiency (EE). Degradation of the Gold Tri.E™ in o/w microemulsion was significantly reduced as compared to the bare Gold Tri.ETM. This suggested that the system could protect Gold Tri.E™ from thermal and hydrolysis degradation. Thus, the ease of preparation, low-cost production, and small particle size obtained when Gold Tri.E™ encapsulated in this system give promising drug delivery system to encapsulate, protect, and increase the shelf life of Gold Tri.E™.

Two-dimensional PtSe2 Theoretically Enhanced Goos-Hänchen Shift Sensitive Plasmonic Biosensors

Platinum diselenide (PtSe2), an emerging two-dimensional transition metal dichalcogenide, exhibits thickness-dependent refractive index, and hence, intriguing optical properties. Here, we employ it as a plasmonic sensing substrate to achieve significant enhancement in Goos-Hanchen shift sensitivity. Through systematic optimization of all parameters, four optimum sensing configurations have been achieved at different wavelengths ranging from visible to near-infrared region, where the Goos-Hanchen shift sensitivity receives four times enhancement in comparison with the conventional bare gold sensing substrate. There is a linear range of Goos-Hanchen shift with the tiny change of refractive index for each optimal configuration. The detection limit of the refractive index change can be as low as 5 × 10−7 RIU which is estimated to be lower by 2 orders of magnitude, and the corresponding sensitivity of biomolecules has a 1000-fold increment compared with that of bare gold-based sensors.

Gas-Phase Deposition of Gold Nanoclusters to Produce Heterogeneous Glycerol Oxidation Catalysts

Gold nanoparticles prepared by colloidal methods are effective catalysts for selective glycerol oxidation under basic conditions. Large-scale synthesis of catalysts by wet chemical methods leads to large amounts of waste and can result in polymer or salt residues remaining on the catalyst. In contrast, gas-phase cluster deposition (cluster beam deposition) offers a solvent-free method to synthesize controlled nanoparticles/clusters. We show that the deposition of bare gas-phase gold clusters onto carbon powder leads to a catalyst comparable to that prepared by colloidal methods. This shows the feasibility of the synthesis method to produce oxidation catalysts with reduced waste.

Radiation-Activated Pre-Differentiated Retinal Tissue Monitored by Acoustic Wave Biosensor.

A thickness-shear mode acoustic wave biosensor operated within a flow-through system was used to examine the response of mouse retinal tissue to radiation. Control experiments conducted with respect to exposure of the bare gold electrodes of the device under various conditions of light intensity and bathing solution yielded reversible changes in resonant frequency (Fs) and motional resistance (Rm). The magnitude of transient changes was proportional to light intensity, but independent of solution type. These alterations in acoustic parameters were ascribed to acoustic coupling phenomena at the electrode-to-liquid interface. Pre-differentiated retina from mouse samples deposited on the thickness shear mode (TSM) electrode exposed to a high light intensity condition also exhibited reversible changes in both Fs and Rm, compared to control experiments involving a coating used to attach the tissue to the electrode. In this case, the radiation-instigated reversible responses for both acoustic parameters exhibited a reduction in magnitude. The changes are ascribed to the alteration in viscoelasticity of the retinal matrix on the TSM electrode surface. The precise biophysical mechanism responsible for the changes in Fs and Rm remains a challenge, given the complex make up of retinal tissue.

Electrochemical Characterization of Redox Probes at Gold Screen‐Printed Electrodes: Efforts towards Signal Stability

AbstractIn this work, three universally used redox probes in amperometric biosensing devices, [Fe(CN)6]3−/[Fe(CN)6]4−, Ru[(NH3)6]3+, and ferrocenedimethanol (FDM), were selected to evaluate the stability of electrochemical signals provide by the reporting systems. Studies were carried out at disposable gold screen‐printed electrode (AuSPE) biosensing platforms, commonly used for screening chemical and biological relevant biomolecules. Firstly, electrochemical combined‐surface plasmon resonance (eSPR) studies were performed to evaluated adsorption reversibility and/or formation of redox probe complexes at the bare gold surface when routinely used electrochemical techniques, namely cyclic voltammetry (CV) and square‐wave voltammetry (SWV), are recorded. Then, the results obtained were compared with those obtained at the AuSPE under the same electrochemical conditions. Based on our findings, best experimental conditions, including the type of electrochemical technique used, are speculated for each reporting system in order to improve the analytical signal stability. Finally, a methodology based on SWV technique was applied to modified electrodes to provide a simple and easy tool to ensure diffusion controlled permeability of probes thorough the films to electrode surface.

Preparing DNA SAM Electrochemical Sensors Using Potential Assisted Deposition Methods. Controlling the Coverage and Local Organization of the DNA in the SAM.

Typically, DNA SAMs used for electrochemical based sensing are prepared without controlling the gold electrode potential[1]. Applying a potential during DNA deposition enables control over the coverage and DNA organization[2-4]. These characteristics are determined by the composition of the immobilization buffer, the immersion time, the DNA concentration, the extent of backfilling with a small alkylthiol and whether deposition occurs on a bare or alkythiol coverage gold surface[3-4]. Few studies have explored the influence of the underlying surface crystallography. Here, we show the possibilities of using electrochemical potential control to manipulate the characteristics of the DNA SAM. Moreover, the use of a single crystal gold bead electrode, coupled with the use of a fluorophore tagged DNA and fluorescence microscopy, enables examination of the influence of the underlying surface crystallography on the DNA SAM prepared. Various constant potentials were used as well as using a square-wave potential perturbation during deposition. There are significant differences in the DNA SAM produced under these conditions. In some cases, the DNA coverage was low on the <111> surfaces, higher on more open or atomically rough regions. In other cases, the coverage was higher on the <100> surfaces as compared to the other regions. The use of constant positive or negative potentials (vs SCE) resulted in significant differences in the relative coverages among regions of different atomic arrangements (Fig 1). In addition, a significant difference was observed between immobilization buffers that contain Cl and those that are Cl free. Also, the use of constant or square-wave potential perturbations resulted in significantly different local organizations of DNA in the SAM. Examples of these types of DNA SAM surfaces will be presented with some conclusions on the implications for use on polycrystalline planar gold surfaces.

Electrocatalytic Metallic Nanostructures Prepared By Electrorefining and Cathodic Corrosion

Metallic nanostructures (NS) due to their unique properties are often used as electrocatalytic electrode materials in energy conversion and storage as well as in sensing applications. Their common methods of preparation involve homogeneous synthesis and electrodeposition from solutions containing appropriate precursor and often reducing agent and capping agent (surfactant). The main drawbacks of these methods are restricted yield, waste production and often intrinsic contamination of the surface of obtained NS. Moreover, surface capping ligands affect electrocatalytic activity by hindrance of reactant access to the active sites.We propose a versatile method of preparation of bare (non-capped) mono- and multi-metallic (Au,1 Cu,2 Ag, Fe) NS by localized electrorefining of polycrystalline raw metals at high efficiency in a controlled manner. Catalytic activities of obtained NS towards oxygen reduction reaction (ORR) in alkaline media, hydrogen evolution (HER) and carbon dioxide reduction (CO2RR) to easily electrooxidizable fuels (formic acid and carbon monooxide) were analyzed by feedback mode scanning electrochemical microscopy (SECM). The morphology and specific activity of obtained NS depend on used support material (indium tin oxide (ITO) and glassy carbon) and other electrorefining parameters such as electrodeposition potential, source velocity and the composition of the electrolyte. The last parameter determines stoichiometry of Faradaic processes. Both gold and copper electrooxidation and electroreduction can follow one electron stoichiometry. ORR in alkaline media and CO2RR occur effectively on NS with highly developed surfaces, containing large number of defects, corners and edges, whereas HER occurs efficiently at crystallographic Cu facets. Bare gold NS also exhibit outstanding plasmonic properties. They were applied as support for surface-enhanced Raman spectroscopy (SERS) of single molecules providing enhancement factor >106.1 Another method of preparation of metallic nanostructures is cathodic corrosion. This approach for platinum was studied by Koper group.3 We used this procedure for platinum ultramicroelectrode treatment. Obtained Pt NS exhibit unique catalytic properties towards electrooxidation of glucose.

Quartz Crystal Microbalance Aptasensor for the Molecular Detection of Dengue Virus

Introduction Dengue fever is the major public health concern in the Philippines and is endemic in all regions of the country in which all serotypes are present[1]. Despite the widespread nature of the virus transmitted by mosquitos, molecular diagnostics have significant limitations. An early diagnosis of dengue may prevent severe clinical complications associated with the infection. A novel genosensor using an aptamer for the detection of dengue virus serotypes 1-4 was demonstrated in this study. Method This genosensor composed of a thiolated aptamer immobilized on a 10MHz gold electrode QCM targeting the 3’ untranslated region of all complete genome sequences of dengue virus available in GenBank[2]. Aptamer concentration, buffer pH and ionic strength of buffer solutions were optimized to achieve the highest sensitivity of the QCM genosensor. Atomic force microscopy [3], electrochemical impedance spectrum (EIS) measurements and cyclic voltammetry (CV) were used to characterize the surface of the QCM electrode prepared[4]. Evaluation of binding kinetics and affinity study of the Aptamer-dengue genome was determined by surface plasmon resonance (SPR)[5]. Results and Conclusions Atomic Force Microscopy (AFM), Electrochemical Impedance (EIS) and Cyclic Voltammetry (CV) have been used to characterize the surface of the PQC electrode. The AFM results indicate that the thiolated aptamer onto the electrode has decreased the roughness of gold surface by forming a uniform layer on the electrode surface. The EIS and CV results indicate that the charge transfer resistance is increased after immobilization of the aptamer onto the bare gold electrodes, indicating that direct S-Au bonding via disulfide moieties and the negative charge of protein have blocked the electrode reaction between Fe (II) and Fe (III). The results showed that the developed aptamer QCM sensor has an optimum concentration range of the target dengue genome is 20–100 mg/ml for hybridization. This work demonstrated the possibility of using an immobilized aptamer on a QCM and other sensor platforms for the direct detection of the RT-PCR products of dengue virus serotypes 1-4.

Polydopamine-based molecularly imprinted thin films for electro-chemical sensing of nitro-explosives in aqueous solutions

A sensitive electrochemical sensor was developed for the detection of nitro-explosives in aqueous solutions based on thin molecularly imprinted polydopamine films. Dopamine was identified in silico, based on DFT (density functional theory) calculations with the ωB97X-D/6-31G* basis set, as the best functional monomer and electropolymerized via cyclic voltammetry (CV) in the presence of carboxylic acid-based structural analogues ('dummy' templates) for two model nitro-explosives: TNT (2,4,6-trinitrotoluene) and RDX (Research Department eXplosive, 1,3,5-trinitroperhydro-1,3,5-triazine). This approach afforded a homogenous coverage of gold electrodes with imprinted films of tunable thickness. The electropolymerized molecularly imprinted polydopamine films allowed for a 105-fold sensitivity improvement over a bare gold electrode based on tracking the redox peaks of the targets by CV. This improved sensitivity is ascribed to the ability of the MIP to concentrate its target in proximity to the transduction element. The MIP films showed reproducible binding in phosphate buffer (10 mM, pH 7.4), with a dynamic range from 0.1 nM to 10 nM for both TNT and RDX and an increased selectivity over closely related structural analogues.

Inhibition of choroidal neovascularization by systemic delivery of gold nanoparticles

Choroidal neovascularization (CNV) is the abnormal growth of blood vessels that sprout from the choroid vasculature and grow beneath and into the retina. The newly formed blood vessels in CNV often leak blood and fluid which deteriorates vision over time, eventually leading to blindness. In the present study, we examined the efficacy of intravenously injected gold nanoparticles in the laser-induced CNV animal model. Using optical coherence tomography (OCT) and fluorescein angiography, we evaluated CNV lesions longitudinally, over a period of 21 days, with and without nanoparticle treatment. Intravenously injected low concentration of bare gold nanoparticles showed significant anti-angiogenic properties by suppressing CNV development and progression. The treatment group showed significantly decreased fluorescein leakage at the CNV site compared to vehicle injected control mice. OCT assisted CNV volume measurement at all time points showed a significant reduction in lesion size in the treatment group compared with controls.

Complex electrical spiking activity in resistive switching nanostructured Au two-terminal devices

Networks of nanoscale objects are the subject of increasing interest as resistive switching systems for the fabrication of neuromorphic computing architectures. Nanostructured films of bare gold clusters produced in gas phase with thickness well beyond the electrical percolation threshold, show a non-ohmic electrical behavior and resistive switching, resulting in groups of current spikes with irregular temporal organization. Here we report the systematic characterization of the temporal correlations between single spikes and spiking rate power spectrum of nanostructured Au two-terminal devices consisting of a cluster-assembled film deposited between two planar electrodes. By varying the nanostructured film thickness we fabricated two different classes of devices with high and low initial resistance respectively. We show that the switching dynamics can be described by a power law distribution in low resistance devices whereas a bi-exponential behavior is observed in the high resistance ones. The measured resistance of cluster-assembled films shows a scaling behavior in the range of analyzed frequencies. Our results suggest the possibility of using cluster-assembled Au films as components for neuromorphic systems where a certain degree of stochasticity is required.